Asturias de Santillana is a historical comarca whose territory in large part corresponded to the central and western part of today's autonomous community of Cantabria, as well as the extreme east of Asturias. Most of the province of Asturias belonged to the comarca of Asturias de Oviedo. Also known also as a merindad and documented since the 13th century, Asturias de Santillana comprised the western part of Cantabria (except Liébana which belongs to another comarca) including the Saja River valley and the Nansa River. Its borders used to go along the coast from the council of Ribadedeva to the municipality of El Astillero (old Camargo Valley), to the shores of the Bay of Santander), which leads to the administrative division of Trasmiera. From the south it went up to the Cantabrian cordill