[3] From the 2nd century AD until the reign of Diocletian (284–305), it was officially known as Alpes Atrectianae et Vallis Poenina, which is attested on an inscription from the Severian period (193–235).

[3] The region of Vallis Poenina, corresponding to the modern Canton of Valais between the Lake Geneva and the Great St. Bernard Pass, was inhabited at the time of the Roman conquest by Celtic tribes known as the Vallenses, namely the Nantuates, Veragri, Seduni, and Uberi.

After the Roman invasion led by Augustus in 16–15 BC, the area was initially placed under military control (praefectus Raetis, Vindolicis, vallis Poeninae) and incorporated into the province of Raetia et Vindelicia, which stretched between the central Alps and the Danube.

[12][13] The Vallensian tribes were granted Latin Rights and grouped together into a single civitas Vallensium during the reign of Claudius (41–54 AD).

According to most scholars, Vallis Poenina was separated from Raetia et Vindelicia and united with the newly created Alpes Graiae, located west of the Little St Bernard Pass and inhabited by the Ceutrones, during the same period.