The kingdom originated in the western and central territory of the Cantabrian Mountains, part of the Gallaecia, particularly the Picos de Europa and the central area of Asturias. The main political and military events during the first decades of the kingdom's existence took place in the region. According to the descriptions of Strabo, Cassius Dio and other Graeco-Roman geographers, several peoples of Celtic origin inhabited the lands of Asturias at the beginning of the Christian era, most notably:
- in the Cantabri, the Vadinienses, who inhabited the Picos de Europa region and whose settlement gradually expanded southward during the first centuries of the modern era
- the Orgenomesci, who dwelled along the Asturian eastern coast
- in the Astures, the Saelini, whose settlement extended through the Sella Valley
- the Luggones, who had their capital in Lucus Asturum and whose territories stretched between the Sella and Nalón
- the Astures (in the strictest sense), who dwelled in inner Asturias, between the current councils of Piloña and Cangas del Narcea
- the Paesici, who had settled along the coast of Western Asturias, between the mouth of the Navia river and the modern city of Gijón
Picture of ḷḷagu del Vaḷḷe
), showing typical Asturian cottages (called teitos
), as already in use in the time of the Astures
Classical geographers give conflicting views of the ethnic description of the above-mentioned peoples. Ptolemy says that the Astures extended along the central area of current Asturias, between the Navia and Sella rivers, fixing the latter river as the boundary with the Cantabrian territory. However, other geographers placed the frontier between the Astures and the Cantabri further to the east: Julius Honorius stated in his Cosmographia that the springs of the river Ebro were located in the land of the Astures (sub asturibus). In any case, ethnic borders in the Cantabrian Mountains were not so important after that time, as the clan divisions that permeated the pre-Roman societies of all the peoples of Northern Iberia faded under similar political administrative culture imposed on them by the Romans.
The situation started to change during the Late Roman Empire and the early Middle Ages, when an Asturian identity gradually started to develop: the centuries-old fight between Visigothic and Suebian nobles may have helped to forge a distinct identity among the peoples of the Cantabrian districts. Several archaeological digs in the castro of La Carisa (municipality of Lena) have found remnants of a defensive line whose main purpose was to protect the valleys of central Asturias from invaders who came from the Meseta through the Pajares pass: the construction of these fortifications reveals a high degree of organization and cooperation between the several Asturian communities, in order to defend themselves from the southern invaders. Carbon-14 tests have found that the wall dates from the period 675-725 AD, when two armed expeditions against the Asturians took place: one of them headed by Visigothic king Wamba (reigned 672-680); the other by Muslim governor Musa bin Nusayr during the Umayyad conquest, who settled garrisons over its territory.
The gradual formation of Asturian identity led to the creation of the Kingdom of Asturias after Pelagius' coronation and the victory over the Muslim garrisons in Covadonga in the early 8th century. The Chronica Albeldense, in narrating the happenings of Covadonga, stated that "Divine providence brings forth the King of Asturias".