Alagna was founded with the expansion of the Walser coming from Macugnaga, who crossed the Turlo Pass. They first occupied the shelters of the herdsmen in the Mud area and the hamlets of Pedemonte and Oubre Rong, and successively the ancient area called Alpe di Alagna or Olen, today Pedelegno. The settlements of alpe d'Otro were however colonies from Gressoney.  With the passing of the years, one by one the other 22 hamlets were created, giving life to the great community at the head of the Sesia Valley.

The story of Riva Valdobbia is different. Older and founded diversely, it was the last village of the valley, inhabited until the year 1200. The village expanded into the whole area surrounding the Sesia river basin with the arrival of the colonies from Alagna. With their expansion, they started to ascend Valle Vogna until they encountered the Walser from Gressoney who, in the meantime, started the colonization of colle Valdobbia.

The integration of the newcomers with the rest of the valsesian populations was rather slow. They remained in contact with their homeland for a long time however, thanks to a tight network of connections via which they imported salt, metal implements, corn seeds and clothes. In 1410 the Walser of Alagna took on the job of putting the mountain pastures to use and paying an annual land rental fee from the tenants of Rocca and Campertogno, thus settling legally in that territory. After this date and the acquisition of vicinity rights, the umbilical cord that still tied them to their homeland atrophied and salt, equipment and basic food stuffs were bartered at the markets in Varallo Sesia with cattle and cheese.