Major professional sports leagues in the United States and Canada

Major professional in the United States and Canada traditionally include four leagues: Major League Baseball (MLB), the National Basketball Association (NBA), the National Football League (NFL), and the National Hockey League (NHL). Other prominent leagues include Major League Soccer (MLS) and the Canadian Football League (CFL).

MLB, the NBA, the NFL, and the NHL are commonly referred to as the "Big Four". Each of these is the wealthiest professional club competition in its sport worldwide, and along with the Premier League, make up the top five sports leagues by revenue in the world.

Each of the Big Four leagues, as well as MLS and the CFL, averages at least 15,000 fans in attendance per game . The NFL has the largest stadiums on average in the world, ranging in capacity from just over 60,000 to almost 100,000 spectators, while MLB ballparks generally hold between 30,000 and 50,000 fans. Venues used primarily by MLS and CFL vary more widely in capacity, from about 20,000 to about 60,000. The two indoor leagues, the NHL and NBA, play mostly in arenas that hold 18,000 to 20,000 seats. There is a significant number of multi-purpose venues that host events in both NFL and MLS (5),Chicago, Atlanta, Seattle, Foxboro and Charlotte CFL and MLS (2),Vancouver and Toronto MLB and MLS (1),Yankee Stadium in New York and NBA and NHL (11).Los Angeles, Dallas, Denver, Detroit, Washington D.C., Toronto, Chicago, Philadelphia, Boston, New York, and Salt Lake City. Teams in MLB and the NFL no longer share stadiums, although there are frequent examples of MLB and NFL teams sharing stadiums in the past. The NFL and MLB also play a limited number of annual games in English Premier League stadiums,Principally Tottenham Hotspur Stadium. and the NFL plays a limited number of annual games in stadiums of Germany's Bundesliga,Specifically Allianz Arena, Deutsche Bank Park, and Berlin's Olympiastadion, the last of which hosts its first NFL game in 2025. and less often plays games in stadiums of Mexico's Liga MX,Specifically Estadio Azteca. Brazil's Brasileirão,Specifically Arena Corinthians, which hosted its first NFL game in 2024. and Spain's La Liga.Specifically Estadio Santiago Bernabéu, which hosts its first NFL game in 2025.

The Big Four leagues currently have 30 to 32 teams each, most of which are concentrated in the most populous metropolitan areas of the United States and Canada. Unlike the promotion and relegation systems used in sports leagues in various other regions around the world, North American sports leagues are that maintain the same teams from season-to-season. Expansion of the league usually occurs by adding newly formed teams, though mergers with competing leagues have also occurred.

Baseball, American football, and ice hockey have had professional leagues continuously for over 100 years; early leagues such as the National Association of Professional Base Ball Players, the Ohio League, and the National Hockey Association formed the basis of the modern MLB, NFL, and NHL, respectively. Basketball was invented in 1891, and its first professional league formed in the 1920s. The Basketball Association of America, founded in 1946, formed the basis of the NBA in 1949 and has lasted for over 75 years.

Soccer was first professionalized in 1894, with past U.S.-based leagues including the American Soccer League (1921–1933) (ASL) and original North American Soccer League (1968–1984) (NASL). Major League Soccer (MLS) was established in 1996.MLSsoccer.com, The expansion, refs, Cascadia: MLS Commissioner Don Garber covers it all in annual address, February 27, 2013, http://www.mlssoccer.com/news/article/2013/02/27/expansion-refs-cascadia-commissioner-garber-covers-it-all-march-soccer-addre ().

With a total attendance of nearly 11 million and an average of over 22,000, MLS has the fifth-largest total attendance and third-largest average attendance, among the sports league in U.S. and Canada , had the seventh-highest attendance among global professional soccer leagues. The top soccer league sanctioned by the Canadian Soccer Association is the Canadian Premier League (CPL).

MLS is unique among U.S. and Canada's major sports leagues in that the teams take part in multiple separate tournaments outside the MLS regular and playoff season; the knockout U.S. Open Cup for United States teams and Canadian Championship for Canadian teams, cross-border/regionalCanada, the United States and Mexico form the North American Zone of CONCACAF; the Leagues Cup is the regional clubs championship for the North America Zone, while the Campeones Cup is a zonal super cup between the champions of the two largest leagues, MLS and the Mexican Liga. Leagues Cup and Campeones Cup and the continental CONCACAF Champions Cup and FIFA Club World Cup.

The CFL has the fourth-highest average attendance of leagues in the United States and Canada, behind the NFL, MLB and MLS. , the CFL's average attendance number was 22,795, continuing a slow upward trend for the league. Its level of play is generally recognized as on the second tier of professional football, with the CFL having a slight advantage in player recruitment compared to second-tier American leagues such as the UFL due to the CFL's longer established history.

• " R" denotes regular-season play.
• " P" denotes playoff(s)/postseason stages.
• " F" denotes Final(s).

The "Big Four" leagues each have revenues that can be many times greater than the payrolls of less popular sports leagues in the two nations. In terms of overall league revenue, the NFL, MLB, and NBA rank as the top three most lucrative sports leagues in the world, with the English Premier League and the NHL ranked at fourth and fifth place.

All of the top four major sports leagues have had television contracts with at least one of the original "big three" U.S. broadcast television networks (ABC, CBS, and NBC) since those networks' early years, indicative of the sports' widespread appeal since their inception, continuing today additionally with Fox. In Canada, the NHL has been broadcast on the Canadian Broadcasting Corporation since 1952. In Canada, there is only one MLB team and one NBA team, and no Canadian NFL team exists; therefore, the U.S. national telecasts for those three leagues are usually simulcast by a Canadian broadcaster.

The NFL has the largest TV contracts, and earns roughly $9 billion annually from its contracts with Amazon, CBS, ESPN, Fox, NBC, and DirecTV for the 2023 through 2033 seasons. MLB earns $1.5 billion annually from its contracts for the 2014 through 2021 seasons with ESPN, Fox, and Turner Sports (TBS).

The NBA's nine-year television deal beginning with the 2016–17 season with ABC/ESPN and TNT generates annual league TV revenues of $2.7 billion. The NBA's next TV deal, set to take effect in 2025–26 and run through the 2035–36 season, will be with ABC/ESPN, NBC, Peacock, and Amazon, and also covers the WNBA for its 2026–2036 seasons. It is expected to generate total annual revenues of $6.9 billion, with a reported split of roughly $6.7 billion for the NBA and $200 million for the WNBA. The NHL's current U.S. television deal with ABC/ESPN and Turner Sports took effect with the 2021–22 season and runs through 2027–28. While the NHL did not announce the amount, outside reports indicated that ABC and ESPN parent company Disney was paying a total of about $400 million and Turner about $225 million annually. This $625 million annual contract for American rights is in addition to the $433 million annual fee Rogers Sportsnet pays for Canadian rights.

All four major sports leagues have launched a network of their own—NBA TV in the U.S. in 1999 and in Canada in 2001, the NFL Network in 2003, the NHL Network in Canada in 2001 and in the U.S. in 2007, and the MLB Network in 2009. All networks remain in operation today except for the Canadian NHL Network, which was shut down shortly before the league's 2015–16 season.

Teams in MLB, the NBA, and the NHL—which play several days per week—negotiate contracts with local broadcasters to air most of their games, both terrestrial networks and regional sports networks. Some teams (such as the New York Yankees) may even partially or fully own the cable network upon which their games are broadcast, and often receive more revenue from local broadcasts than any other source. NFL teams, which generally play once per week, do not negotiate local broadcast contracts, but are allowed to negotiate their own television deals for preseason games with syndication and broadcast stations.

The current MLS broadcast deals took effect with the 2023 season. The league's primary media partner is Apple, which paid a reported $2.5 billion for exclusive worldwide streaming rights from 2023 to 2032. All league games are streamed on the MLS Season Pass service on Apple TV+. English and Spanish commentary are available for all matches, and games involving Canadian teams are also available in French. Linear television rights for 2023–2026 are held by Fox Sports in both English and Spanish in the US, and the English-language TSN and French-language RDS in Canada.

Before the Apple TV+ deal, MLS matches were shown in English on ESPN and Fox Sports, and in Spanish on Univision. MLS's eight-year contracts for U.S. rights for the 2015–2022 seasons earned a combined $105 million annually.

The CFL's current television deal with TSN pays the league at least $50 million per year until 2026. Its American broadcast contract with CBS Sports Network pays $1 million per year for 34 of the league's 81 games; prior to its deal with CBS Sports Network, the CFL had bundled its TSN rights with ESPN (a minority owner of TSN), who contributed a negligible $100,000 to the annual rights fees. The remainder of the CFL's games are carried online in the United States for free.

Since 2002 expansion franchises have commanded huge entry fees, which represent the price the new team must pay to gain its share of the existing teams' often guaranteed revenue streams. The Houston Texans paid $700 million to join the NFL in 2002. By comparison, the Charlotte Bobcats (now the Hornets) paid $300 million to join the NBA. The Arizona Diamondbacks and Tampa Bay Rays (originally Devil Rays) paid $130 million each to join MLB. The NHL's Seattle Kraken (which started play in 2021), paid $650 million to join the league, a 30% increase from the $500 million paid by the Vegas Golden Knights to join the league in 2017. The Golden Knights' fee was a dramatic increase from the $80 million paid by each of the previous two teams to enter the NHL, the Columbus Blue Jackets and Minnesota Wild. Two of the six most recently announced Major League Soccer expansion teams, 2019 entrant FC Cincinnati and 2020 arrival Nashville SC, each paid a $150 million expansion fee, a significant increase from the $100 million that New York City FC paid to join MLS in 2015. The 29th MLS team, ultimately unveiled as 2022 entry Charlotte FC, reportedly paid $325 million. The 30th and most recent expansion team San Diego FC paid $500 million in 2023. For comparison, the Ottawa Redblacks paid C$7 million to join the Canadian Football League.

Relocation of teams is generally uncommon compared to minor leagues. However, all of the top four major leagues have had at least one franchise relocate to another city since 2004. Among the Big Four leagues, the NFL has had the most relocations occurring recently, relocating three teams over the course of the late 2010s. The NHL is the most recent of the Big Four to expand, having added the Vegas Golden Knights in 2017, the Seattle Kraken in 2021, and the Utah Hockey Club (now the Utah Mammoth) in 2024. None of the other Big Four leagues have added expansion teams since 2004.

In the fifty years between 1903 and 1953, MLB experienced no franchise changes—no new franchises, no franchises ceasing operations, and no franchises moving—marking the longest such period of stability of any Big Four league.

In contrast to the Big Four leagues, MLS has operated on a policy of continuous expansion since 2005. After bottoming out at 10 teams in 2004, it has never gone more than two seasons without adding one or two expansion teams. , MLS tripled in size from its 2004 minimum, with 30 teams. The league has contracted three teams in its history: teams in Miami Fusion and Tampa Bay folded in 2002, and the Los Angeles-based Chivas USA squad folded in 2014. MLS has had one franchise relocate, the San Jose Earthquakes, which became Houston Dynamo FC in 2006; the Earthquakes returned as an expansion club in 2008, inheriting the pre-relocation history of the original Earthquakes.

All seven CFL franchises geographically between Vancouver and Toronto have been in place since the BC Lions were founded in 1954. The league has had problems in the two markets east of Toronto; both Montreal and Ottawa have each seen two CFL teams fail since the 1980s, although both cities have active teams as of the 2014 season. The cities are now represented by the Alouettes and Ottawa Redblacks, respectively. Among existing teams, none has ever formally relocated from one city to another; the Alouettes, however, inherited a management structure from the Baltimore Stallions, a team from the league's unsuccessful 1990s-era South Division. The CFL has had either eight or nine teams in operation since its inception except for the 1994 and 1995 seasons in which the league temporarily expanded into the United States.

All of the top four major leagues grant territorial exclusivity to their owners, precluding the addition of another team in the same market unless the current team's owners consent, to avoid competition for ticket sales and television rights. Agreements to share are market are generally obtained in exchange for compensation, residual rights, or both. For example, to obtain the consent of the Baltimore Orioles to place an MLB team in Washington (about away), a deal was struck under the terms of which television and radio broadcast rights to Nationals games are handled by the Orioles franchise.

, 49 metropolitan areas (42 in the U.S., seven in Canada) have at least one team in the Big Four leagues. Austin FC, which started play in 2021, is the first and only MLS team in a market not also occupied by at least one Big Four team. The CFL has one team, the Saskatchewan Roughriders, in a market not served by any other major league (the Hamilton Tiger-Cats, while having their city to themselves, are on the outskirts of both the Niagara Frontier (less than 50 miles from Buffalo) and the extended Greater Toronto Area). The newest market any of the Big Four leagues has entered is the Las Vegas Valley, which received the Vegas Golden Knights in 2017 and the Las Vegas Raiders in 2020.

Major leagues tend to place franchises only in the largest, most populated metropolitan areas. Most major league teams are in metropolitan areas having populations of more than 2 million. All but 12 continental U.S. metropolitan areas with a population of more than 1 million host at least one major sports franchise. All five U.S.-based major leagues each currently have at least two teams in both the New York/North Jersey area and the Los Angeles/Anaheim market. MLB, which historically (as a result of its history as two rival leagues) had a team in each component league in Boston, Philadelphia and St. Louis up until the mid-20th century, and in the San Francisco Bay Area until the Athletics move from Oakland to Las Vegas following the 2024 season, still has separate AL and NL teams in Chicago. Twelve American metropolitan areas have a complete set of one or more teams in each of the Big Four leagues; of these, only Detroit does not have an MLS team.

MLB, more than any other major league, focuses its teams in the largest markets. MLB is the only major league that does not have any teams in markets with fewer than 1.75 million people; both it and the NFL have teams in every U.S. market with over 4 million people. The NHL is the major league that least follows the general trend, due to the fact that a disproportionate number of its franchises are in cities with cold winters. The NHL lacks teams in a number of southern metropolitan areas with populations of over 3 million (Houston, Atlanta, San Diego) but has five teams in northern metropolitan areas with fewer than 1.25 million people, all of which are in or adjacent to Canada (the lone American team in a metro area of that size being the Buffalo Sabres). While only one MLB team, the San Diego Padres, is located in a market that has no other major league teams, five NBA teams are located in cities devoid of any additional "Big Four" franchises: the Memphis Grizzlies, Oklahoma City Thunder, Orlando Magic, Portland Trail Blazers, and San Antonio Spurs. A sixth NBA team, the Sacramento Kings, will share its market with the former Oakland Athletics from 2025 until the latter team moves to Las Vegas in 2028. Three of these NBA-only cities (Memphis, Oklahoma City, San Antonio) and Sacramento also lack an MLS team. The Salt Lake City market, home to the Utah Jazz (as well as MLS team Real Salt Lake), lacked another major-league team before the Utah Mammoth after the 2023–24 season.

The NFL has one major exception. The Green Bay Packers survive in major league sports' smallest metropolitan area (300,000 population) thanks to unique nonprofit corporate ownership, proximity to the neighboring Milwaukee market (giving a combined metro area of over 2 million), a league business model that relies more heavily on equally distributed television revenue that puts small-market teams at less of a disadvantage, and the loyalty of their Cheesehead fan base, whose fans and their next of kin typically renew their season tickets every year until their issue expires, resulting in a centuries-long waiting list for season tickets. Green Bay is one of two NFL teams, the other being the Jacksonville Jaguars, that are the only major league franchises in their metropolitan area.

Both MLB and the NFL have had two prolonged recent exceptions in which the league was absent from one of the U.S.'s ten most populous metropolitan areas; from 1972 to 2004, ninth-place Washington, D.C., had no MLB team, and from 1995 to 2016, second-place Los Angeles had no NFL teams.

The NHL's national footprint is a relatively recent situation. Historically, the league was concentrated in the northeast, with no teams south of New York City or west of Chicago from 1935 until 1967. The league expanded its footprint westward in a 1967 expansion but, other than the unsuccessful Atlanta Flames, avoided the South until making a major expansion into the territory in the 1990s.

Both the NBA and MLS have higher concentrations of teams in the western United States than the other major leagues. Whereas the NBA's teams tend to be somewhat more evenly distributed across the United States, MLS's presence in areas of the southern United States has historically been sparse; after MLS folded its two Florida-based teams after the 2001 season, it did not re-enter the South until Orlando City SC joined the league in 2015, with Atlanta United FC following in 2017. With the addition of Minnesota United FC in 2017 and Inter Miami CF in 2020, along with the departure of the NHL's Arizona Coyotes from Phoenix in 2024, MLS has a team in every market with a complete set of teams in each of the Big Four major leagues except Detroit.

The CFL had a total of six teams in the United States over a three-year period between 1993 and 1995, all in medium-sized markets that lacked an NFL team at the time. Of the seven markets those teams occupied, three (Baltimore, San Antonio and Sacramento) had other major league franchises at the time, and two later received a major team (Memphis and Las Vegas). The league also played occasional games in the United States in the 1950s and 1960s.

The largest metropolitan area without a major professional sports franchise depends on the definition of "metropolitan area". Among areas defined by the United States Census Bureau as Metropolitan Statistical Areas (MSAs), California's Inland Empire is the largest without a major franchise. However, it is part of Greater Los Angeles, a region defined by the US Census as a Combined Statistical Area (CSA), and is thus part of the Los Angeles television market. The largest CSA without a major franchise is the Hampton Roads area of southeastern Virginia, spilling over into a small part of North Carolina. The largest TV market without a major franchise is the Hartford–New Haven market, covering all of Connecticut except the former Fairfield County; Hartford's last major league squad, the NHL's Hartford Whalers, left in 1997.

The Canadian Football League has teams in all seven current NHL markets, in addition to Hamilton, Ontario, and Regina, Saskatchewan. At least eight of these nine markets have hosted CFL teams every year since the league's officially listed inception in 1958, and no other Canadian market has ever had a CFL team of its own. A conditional expansion franchise was awarded to the Atlantic Schooners in 1982; it folded before ever playing a game. Another bid for a Schooners franchise by Schooners Sports and Entertainment in the late 2010s also failed.

The first Major League Baseball team in Canada was the Montreal Expos, who began play in 1969. In 2005, they moved to Washington, D.C., and became the Washington Nationals. The Toronto Blue Jays, who began play in 1977, became the first team outside the United States to win the World Series in 1992 and 1993.

The Toronto Huskies were a charter member of the Basketball Association of America in 1946, but that team only lasted one season. The NBA expanded into Canada in 1995 when the Vancouver Grizzlies and the Toronto Raptors joined the league. The Grizzlies moved to Memphis in 2001.

MLS has teams in Vancouver, Toronto FC, and Montreal.

The NFL is the only major league to have no team based in a Canadian city; the closest teams to Canada are the Buffalo Bills and Detroit Lions, both representing cities located on the U.S.–Canada border. The Lions play in downtown Detroit, from Windsor, Ontario. The Bills' stadium is located south of the Canada–U.S. border. From 2008 to 2013, the Bills played 8 games in Toronto as part of the Bills Toronto Series which included one regular season game per year. On August 22, 2019, the Oakland Raiders played the Green Bay Packers in a preseason game at the Winnipeg venue now known as Princess Auto Stadium.

With the exception of the NFL, every other major league has had at least one case since 2000 where the league itself has taken ownership or control of a franchise:

• MLB – Purchased the Montreal Expos in 2001 and moved the franchise to Washington, D.C., as the Nationals in 2005 before selling the team to a local group in 2006. MLB also took over the operations of the Los Angeles Dodgers in 2011, citing financial and governance issues stemming from the divorce of the team's co-owners, before Frank McCourt sold the Dodgers to an ownership group in March 2012.
• NHL – Took over the Buffalo Sabres in 2002 after owner John Rigas was arrested for embezzlement, and sold the team to Tom Golisano in 2003. The NHL also seized the Arizona Coyotes in 2009 to prevent its owner from selling it to a buyer who intended to relocate the team, and sold the team to a Phoenix-area group in 2013. The league again took over the Coyotes and sold them to a new owner in 2024, facilitating the franchise's inactivation and activation of the Utah Mammoth.
• NBA – Purchased the New Orleans Hornets from its owner in December 2010, and sold the team to owner Tom Benson in April 2012.
• MLS – Purchased Chivas USA from Jorge Vergara in 2014 and folded the team after the 2014 season. A new L.A. franchise, Los Angeles FC, began play in 2018 as an expansion team and did not inherit Chivas USA's history.
• CFL – Seized the Ottawa Renegades from owner Bernard Glieberman in 2006, suspended the franchise, then sold it to Jeff Hunt, who reactivated it in 2014 as the Ottawa Redblacks. The CFL also accepted ownership in 2019 of the Montreal Alouettes from owner Robert Wetenhall in order to keep it operating until the league announced Sid Spiegel and Gary Stern as the team's new owners in January 2020. The CFL again assumed ownership of the Alouettes in February 2023 following Spiegel's death, and sold the franchise to Québec businessman Pierre Karl Péladeau the next month.

The NFL (nor any of its predecessors) has not taken over operations of any team since 1962, when the American Football League took over the nearly bankrupt Titans of New York in an effort to prevent the team from folding; in 1963, a new ownership group bought the franchise and it became the New York Jets.

The NFL has stronger ownership restrictions than other leagues. The NFL forbids ownership by groups of over 24 people or publicly traded corporations, except the grandfathered Green Bay Packers. Additionally, the league requires that at least one member of the ownership group hold a 30% interest, with stringent limits on the amount of debt that a new ownership group can take on. The NFL also forbids its owners from owning any other professional American football teams; this rule has not always been in place (as the NFL owners previously owned minor league teams in the 1940s) but was in place by the 1980s, when the DeBartolo family was scrutinized for owning both the San Francisco 49ers and USFL's Pittsburgh Maulers (as different members of the family owned each team, the league allowed the DeBartolos to keep the 49ers). Arena Football League teams playing in the NFL team's home market were exempt from this rule during that league's existence. NFL owners were long prohibited from owning major league baseball, basketball and hockey teams unless they were in the NFL team's home market, or not located in other NFL cities. This last set of restrictions was lifted in October 2018; many owners believed that cross-ownership restrictions had outlived their purpose, and they had largely been disregarded since Stan Kroenke, who purchased the then-St. Louis Rams and moved them to Los Angeles while simultaneously owning assets in Denver, became a majority NFL owner in 2010. Additionally, media reports theorized that the cross-ownership ban materially reduced the sale price of the Carolina Panthers earlier in 2018, with several NBA team owners reportedly interested in bidding but barred by then-current NFL rules. The cross-ownership restrictions originally covered soccer, but a 1982 federal court decision in a lawsuit filed against the NFL by the original NASL went in favor of the NASL, thereby exempting soccer from these restrictions.

MLS has adopted a different league structure and operates as a single-entity league, a structure that survived a lawsuit from the players in Fraser v. Major League Soccer. During the first few years of the league, MLS for the sake of stability allowed individuals to operate multiple teams. MLS ownership arrangements have evolved, however; each of the league's current 30 teams is now controlled by a separate ownership group, and no group member has a stake in more than one team.

Five out of nine clubs in the CFL are held by some form of partnership or corporation; of those, one (Saskatchewan Roughriders) is a publicly held corporations in and of themselves, two (Toronto Argonauts and Hamilton Tiger-Cats) are partially owned by public conglomerates, and two (Calgary Stampeders and Ottawa Redblacks) are held by closely held partnerships. Three (BC Lions, Montreal Alouettes, and Edmonton Elks) are held by an individual owner. The ninth team, the Winnipeg Blue Bombers, operates under the shell of the Winnipeg Football Club, a nonprofit sports club with no clear ownership structure or share capital.

Baseball's National League withstood three challenges in its first quarter century of existence. The American Association began in 1882 in several lucrative markets without an NL team. For several years, the AA was a viable competitor to the NL, and the NL and AA champions competed in an informal World Series. Four of the AA's teams defected to the NL in its later years, before the AA expired in 1891. Labor problems led to the formation of the Players' League for the 1890 season; it attracted a significant percentage of the baseball talent and caused the NL and AA significant financial harm, but it lacked financial backing and folded after only one season. The minor Western League moved several franchises in NL cities and cities abandoned by the NL for the 1900 and 1901 seasons, and renamed itself the American League in direct competition with the NL. The NL and AL made peace in 1903; the resulting agreement formed what today is known as Major League Baseball. MLB withstood the challenge of the Federal League in 1914. Various Negro leagues peaked from the 1920s to the 1940s, and on barnstorming tours the Negro league players showed themselves to be MLB players' competitive equals, but after Jackie Robinson broke the color barrier in 1947, the influx of black stars into the major leagues drained the Negro leagues of talent. MLB prevented the Continental League from getting off the ground in 1961–62 by placing teams in four of that league's proposed cities by either expansion or relocation.

The NFL has fought off the most rivals throughout the years, and to this day faces a competing start-up league every few years. One strong rival to the NFL was the All-America Football Conference of 1946–1949; three of their seven teams merged with the NFL for the 1950 season, and two of the three still exist in the NFL. Four (all unrelated) rivals were named American Football League; the last American Football League existed from 1960 to 1970, winning the last two of the four pre-merger Super Bowl games, before merging with the NFL in 1970. The NFL has beaten back other significant rival football leagues, often placing expansion or relocation teams in those cities following that league's demise: the World Football League of 1974–1975 (the NFL added two teams in 1975), the United States Football League of 1983–1985 (the NFL relocated one team to a USFL market in 1988), and the Canadian Football League's American franchises of 1993–1995 (the NFL added three teams in the mid 1990s, including one in the CFL's most successful U.S. market). All told, 13 of the NFL's current 32 franchises were absorbed from a rival league—all 10 AFL franchises of the 1960s, two from the AAFC, and one from the 1936 AFL.

The NBA was formed in 1949 after three years of competition between the large-market Basketball Association of America (from which the NBA traces its existence) and the industrial-based National Basketball League. The NBA also had to fend off two incarnations of the American Basketball League, the first being an Eastern circuit that predated the NBA, and the second existing from 1961 to 1963, after Abe Saperstein was repeatedly denied an NBA expansion team. The NBA later fought off the challenge of the American Basketball Association from 1967 to 1976, in part by expanding from nine to eighteen teams. The NBA then absorbed four of the ABA's most successful franchises in a 1976 merger, and adopted several of the ABA's rule variations, most notably the three-point shot.

The NHL began its existence competing with the Western Canada Hockey League and its predecessor, the Pacific Coast Hockey Association; both had folded by 1926, leaving the NHL as the sole major North American hockey league. The NHL fended off two challenges in the 1960s and 1970s. The NHL prevented the Western Hockey League from achieving parity in the quality of players, salaries and attendance by doubling in size from six to twelve teams in 1967, including into the WHL markets of Los Angeles and San Francisco, and added two more teams in 1970, including a former WHL team in Vancouver. During its existence from 1972 to 1979, the World Hockey Association challenged the dominance of the NHL. The WHA initially attracted stars by offering higher salaries than the NHL and successfully invalidating the NHL's reserve clause, forcing NHL teams to keep up. The bidding war brought financial distress to both leagues. With the WHA and several NHL teams faced with collapse, the NHL negotiated a merger of the leagues whereby the four strongest WHA teams joined the NHL.

The CFL has been historically protected from the competing leagues that the NFL faced, in part because of threats of parliamentary legislation to stop any CFL competitor from being allowed to play in Canada. The Canadian Football Act, proposed in 1974 but never passed, would have given the CFL a government-endorsed monopoly on professional gridiron football in Canada by prohibiting any other league from playing its games in the country; the mere introduction of the bill in Parliament prompted the WFL's Toronto Northmen to move to the United States before playing a single game and later the first USFL was discouraged from establishing teams in Canada with the threat to reintroduce the Act in 1982. In the context of the modern North American sports market as a whole, however, CFL has faced and survived numerous challenges from upstart US-based leagues seeking to establish themselves as a second-tier gridiron football league relative to the NFL and thus competing with the CFL for player talent and consumer exposure. The vast majority of these leagues (such as the first and second USFL, second and third UFL, XFL and its later reincarnation, and AAF) have all been short-lived; all but the current UFL have folded, with that league having formed in advance of the 2024 season by the merger of the 2020s incarnations of the USFL and XFL. Similarly, the CFL itself played the role of a competitor to the NFL during its mid-1990s expansion out of Canada and into the US market, which was also short-lived.

A major factor in this development was the greater distances between cities, with some teams separated by at least half the continent, which in turn resulted in higher traveling costs. When the National League of Professional Base Ball Clubs was established in 1876, its founders judged that in order to prosper, they must make baseball's highest level of competition a "closed shop", with a strict limit on the number of teams, and with each member having exclusive local rights. This guarantee of a place in the league year after year permitted each club owner to monopolize fan bases in their respective exclusive territories and give them the confidence to invest in infrastructure, such as improved ballparks. This in turn guaranteed the revenues needed to support traveling across the continent. With the introduction of TV exposure and other sources of increased revenue during the 20th century, team owners have no incentive to risk giving up this annual income in favor of establishing an "open shop system" where they could be relegated to a lower league that does not generate that kind of lucrative money. There has been discussion of Major League Soccer adopting promotion and relegation, but MLS is not pursuing the option. Eight current MLS teams—Seattle Sounders FC, Portland Timbers, Vancouver Whitecaps FC, CF Montréal, Orlando City SC, Minnesota United FC, FC Cincinnati, and Nashville SC—were promoted from lower leagues through the traditional expansion process, without regard to on-pitch record; instead new teams are brought into MLS based on the financial strength of their ownership and market. Sacramento Republic FC was scheduled to become the ninth such MLS team in 2023 until Ron Burkle pulled out of the expansion deal.

The vast majority of MLB players are developed through the minor league baseball system. Prospective players generally are drafted, and are then assigned to the appropriate minor league level for development. With the growth of college baseball, more players opt to play at the collegiate level and delay entry into the MLB draft; college baseball players with professional aspirations will usually also play collegiate summer baseball to gain experience and exposure while maintaining their college eligibility. Individual teams' large scouting staffs have given way to smaller staffs and subscriptions to commercial player scouting services. Entering the majors directly from high school or college is rare, and most of the few that have were quickly reassigned to the minors. MLB clubs also sign many players from Latin American countries, and have also recruited many players from the Japanese leagues.

Most of the NBA's talent comes from college and high school basketball, although minimum age rules have ended the NBA's practice of drafting players directly from high school beginning in 2006. The NBA's developmental league, now known as the G League, was implemented in 2001 by the NBA to perform the role of a farm system in helping with player development and market reach, but NBA teams more frequently recruit talent from overseas professional leagues, mostly in Europe with a few players being recruited from leagues in Latin America, China, and Australia. Prior to the development of the G League, the Continental Basketball Association had served as a minor league to the NBA.

The National Football League is the only one of the four major sports leagues that does not have a formalized farm system. The source for almost all NFL players is college football, but NFL also has International Player Pathway Program for potential international prospects. Drafted players from college immediately join the main team; if they fail to make the regular season roster, a limited number of players may be assigned to the practice squad. NFL teams rarely recruit players from other gridiron football leagues. American football also has the least global reach for prospects, with one exception being several players from other codes of football primarily as kickers and punters. The league's teams backed the World League (later known as NFL Europe) in the 1990s and 2000s, and purchased teams in the Arena Football League for a period in the 2000s. As of 2019, the National Football League Players Association explicitly opposes having an official minor league in the same model as the other major sports, mainly because of the risk of injury. The current version of the United Football League has positioned itself as a de facto minor league and opportunity for players to reach the NFL while asserting its independence as an organization. The NFL does operate two overseas youth academy, one in England at Loughborough University and the other in Australia at A. B. Paterson College.

Each NHL team has an affiliate in North America's top-tier minor hockey league, the American Hockey League, and most have an affiliation with teams in the ECHL. For decades, the traditional route to the NHL has been through junior hockey and the Canadian Hockey League (CHL). Beginning in the 1970s, NHL teams began drafting and signing prospects from Europe, and a growing number of NHL hopefuls are forgoing the CHL in favor of NCAA Division I college hockey. Additionally, USA Hockey also sanctions junior hockey leagues, such as the United States Hockey League and North American Hockey League, that allow players to develop while also retain NCAA eligibility in order to make the NHL. Almost all draft picks are initially assigned to an affiliate in their NHL team's minor league system for development.

MLS teams sign players from their youth academy, from the MLS SuperDraft, and from overseas. MLS teams rely on their youth academies, which are now a requirement for all MLS clubs. MLS clubs can operate youth teams as young as 13–14 years old. Some youth academy teams participate in lower-tier leagues. MLS also holds an annual draft in which top college soccer players are selected. MLS has in the recent past had a formal relationship with the United Soccer League, which operates (among other leagues) the Division II USL Championship (USLC) and Division III USL League One (USL 1). For several years in the 2010s, MLS teams were nominally required to field a reserve team in a USL league, either by direct ownership or affiliation with a separately owned team, although this requirement was never strictly enforced. MLS relaunched its reserve league in 2022 as MLS Next Pro, a third-level league that initially featured 20 MLS reserve teams and one independently owned team (Rochester New York FC, which folded after Next Pro's first season). Of the 30 current MLS teams, all but CF Montréal, D.C. United, and San Diego FC field reserve sides in Next Pro. This setup allows developing MLS players to gain playing experience.

The CFL's draft is limited to Canadian citizens, plus non-citizens who were raised in Canada. In addition to university/college football, the CFL draft also draws players from the long-established Canadian Junior Football League and its component leagues. The league also draws from the same pool of free agents as the NFL, with players who do not make the NFL often going north to seek work in the CFL. The CFL requires free agents to sign contracts, and thus stay in the league, for a minimum of two years. Unique to the CFL is the concept of the negotiation list, which allows CFL teams to unilaterally declare exclusive rights to any given player. Described as an "enduring mystery", the negotiation list forces players to accept the offer they are given, usually at league minimum, with no leverage to negotiate with other teams; there is no order or limits to the negotiation list, and teams can add or remove players to a 45-position negotiation list without their permission and at any time, regardless of age. Since 2018, ten of the 45 players must be publicly announced.

The average annual salary for players in the four major leagues is about US$2.9 million in 2008, although player salaries can range from $500,000 for backup players to as much as $40 million (up to around $60 mil in the NFL and the NBA by 2021, not counting endorsements and sponsorship deals) for .

NFL, MLB, and NBA have the biggest and longest contracts in the history of professional sports.

NBA players have the highest average player salaries of the four leagues; however, their teams also have the smallest rosters.

The NFL has the highest average team payroll. However, 55-player NFL rosters are far larger than the other three leagues'. Many players on NFL rosters see little actual game play, and teams play far fewer games, making their players on average the lowest paid of the Big Four leagues. After a brief lockout during the 2011 off-season, league owners and the NFLPA signed a new collective bargaining agreement that imposed a hard salary cap of $120 million in the 2011 season, but temporarily suspended the salary floor, which returned in the 2013 season at 89% of the cap.

MLB is now alone among the major leagues in that it lacks any form of a salary cap and has enacted only modest forms of revenue sharing and luxury taxes. Compared to the other leagues, there is a far greater disparity between MLB payrolls. The New York Yankees had the highest payroll of any American sports team in 2006 when they paid $194 million in players' salaries – nearly twice the NFL salary cap and nearly thirteen times the payroll of the Miami Marlins who spent about $15 million (significantly less than the mandatory minimum team payrolls in the NFL and NHL).

For the 2010–11 NHL season, the average player salary was slightly above the pre-lockout level of US$1.8 million. In the same season, the league's salary cap was US$59.4 million per team, with the salary floor set at US$16 million under the cap. For the , the cap has been set as US$79.5 million, with the floor at US$58.8 million.

MLS has lower average salaries and smaller payrolls than the other leagues. MLS kept a strict rein on player salaries until 2007, when MLS introduced the Designated Player Rule, which allows MLS teams to pay higher wages for star players. David Beckham was the first player signed under this rule. The highest MLS payroll in 2024 was Inter Miami CF with $41.7 million, while CF Montréal spent the lowest at $11.4 million. The league's average salary was $596,226 per year. MLS' minimum player salary will increase from $63,542 to $85,502 for most players.

The CFL has a relatively smaller annual player salary and salary cap compared to the other leagues. The average salary in 2018 is $113,000 and the salary cap in 2018 is CAD $5.2 million.. As recently as the 1990s, loopholes in the salary cap allowed CFL teams to pay select marquee players a salary comparable to their NFL counterparts, but financial problems forced the league to close those loopholes. Starting quarterbacks, typically the highest paid players on a CFL roster, can make as much as CAD$750,000.

there have been 31 occasions in which all of the Big Four leagues played games on the same day, an occurrence popularly termed a '''sports equinox'''. Typically occurring on a Sunday, Monday or Thursday in October or early November due to the NFL's scheduling windows, the first sports equinox occurred on October 17, 1971, when the 1971 World Series went to a Game 7 and landed on a Sunday with a full slate of 12 NFL games, three NHL games and six NBA games. Including that day, ten sports equinoxes occurred between 1971 and 1985, but only one between then and 2009. The phenomenon became a regular occurrence from 2010 onward, and at least annually since 2015. Additionally, MLS is beginning the MLS Cup Playoffs; it has scheduled playoff games on the day of a sports equinox since 2021. The most recent sports equinox took place on October 28, 2024, with two MLS Cup Playoff games, Game 3 of the 2024 World Series in MLB, a ''Monday Night Football'' game in the NFL, 11 NBA games and 8 NHL games. The CFL is near the end of its regular season and beginning the playoffs during this window. As for a super sports equinox where a single city's teams in each league all play on the same day, only two have happened: November 4, 2001, in the Phoenix area for the Big Four (which involved the Arizona Diamondbacks at the 2001 World Series, and regular season games involving the Arizona Cardinals, [[Phoenix Suns]], and [[Phoenix Coyotes]]) and October 28, 2018, in the Los Angeles area for the Big Four and MLS (which involved the Los Angeles Dodgers at the 2018 World Series, and regular season games for the [[Anaheim Ducks]], Los Angeles Kings, Los Angeles Rams, [[LA Galaxy]], and Los Angeles Clippers).[https://fivethirtyeight.com/features/the-sports-equinox-is-upon-us/ FiveThirtyEight] Notably, the Los Angeles super sports equinox is the only one where all teams played at home, as the Coyotes were on the road during the Phoenix super sports equinox in 2001.