 On arrival of the Romans in this area (1st Century AD), It belonged to the territory of Autrigones tribe.The current shire of Montes de Oca, where is Halariza, Alariza or Alarcia, was repopulated mainly by Astur, Cantabri, Visigothic and Vascones (Basques) origins in the mid-ninth century, although remained border between the County of Castile with the Caliphate of Córdoba and its allies for at least a century.The shire was afterwards border between kingdom of Castile and the kingdom of Navarre till the mid-twelfth century.