Human presence on the territory dates back to ancient times. In fact, human settlements belonging to the Middle Palaeolithic Age have been discovered in the karst grottoes of the Fenero Mount, an important archaeological area not far from Borgosesia in the Lower Sesia Valley.
Signs of settlements have been unearthed, relating to the Celts, a proud and warlike population, followed by the Roman domination bringing structures and institutions. From the Mediaeval period, we find the Longobards, Franks, Counts and various Signoria, who established an oppressive feudal domination; however the valley always managed to maintain a significant and dignified independence.
The Walser populations started to migrate to the Alagna area around the XIII century, initially from Macugnango and then to the Otro Alps from Gressoney. Alagna still boasts some of the most well preserved Walser architecture.
At the dawn of the XIV century, life in the valley was animated by the presence of Frà Dolcino and his followers, who were engaged in a struggle against the temporal power of the Catholic Church and the clergy in general. Accused of being heretics, they found refuge in Campertogno and then in Rassa. They fought against the militia sent by the Pope, but as Frà Dolcino was a great strategist and soldier, they won the various battles, including the Camproso battle (Campo Rosso), which took place on the plain in Campertogno. After this battle, for unknown reasons the Dulcinians moved from their refuge in the Artogna valley, to the bare rock face above the hamlet of Quare (Campertogno). In March in 1306, after a particularly harsh and cold winter, apparently after a betrayal (also mentioned by Umberto Eco in the “Name of the Rose”), the Dulcinians were attacked by Papal soldiers and forced to abandon their refuge and flee to the Biella region through the Vasnera pass, settling on the Ribello Mount. Here, in the spring of 1307, they were finally defeated: Dolcino, his partner Margherita and his trusted lieutenant were captured, tortured and publicly burnt at the stake in Vercelli.
Successively, the valley fell under the power of the Duchy of Milan and experienced demographic growth. Campertogno was the biggest town of the valley and in the XVII century counted a population of 2700 inhabitants!
In 1707, it was annexed to the Savoy Duchy. In 1798, the Savoy kingdom was invaded by Napoleonic forces. However, the Sesia Valley upon the strength of its recognized independence since 1415 became an exception and the Sesia River was appointed as the border between France and Italy. Indeed, the ancient stone bridge on the river in Campertogno, still today bears the signs of a sentry box (now site of a Virgin Mary painting) which once housed the border guard corps: France on the right bank and Italy on the left bank of the Sesia River, looking downriver.
After the Napoleonic wars, with the separation from the Valsesia Universitas community, it lost all time-honoured privileges, giving rise to a gradual economic crisis and depopulation.