Siero

 ( Municipalities In Asturias ) 

Siero would not be referenced in writing until 905, when Alfonso III granted the church of San Martín de Siero to the Oviedo Cathedral. Other churches in the municipality were also donated to the Oviedo Cathedral throughout that century. There are also records of Hospital and Leper colony being constructed in the area 12th and 13th centuries; some of those continued operating until roughly the 18th century. On 14 August 1270, King Alfonso X granted the area its municipal charter, giving the area official recognition. Eighty years later, the region was split following the death of Alfonso XI, with Pedro I controlling Samartindianes and the rest of the region subject to Enrique II of Trastámara. Following Enrique II's ascent to the throne of Castile, he exempted Siero from taxes due to its inhabitants' support during the Castilian Civil War.

In the early 19th century, Siero was invaded multiple times by the French during the Napoleonic Wars, until the French withdrew from Asturias in 1812. Throughout 20th century, due to the growth of the Coal mining in the region, Siero became one of the fastest growing municipalities in Asturias, more than doubling its population from the beginning of the century to the end. In modern times, the tertiary sector has become Siero's largest, with construction and dairy farming still remaining relevant.

Siero currently consists of the following 29 parishes:

• List of municipalities in Asturias

• Concejo de Siero