The ancient history of San Ponso is recorded almost exclusively in stone.
The presence of numerous tombstones, including four in white marble, carefully engraved, alongside other stelae of Gallic tradition, confirms the intense process of Romanisation in San Ponso.
Information regarding the Lombard period, to which the parish church dates, is rather fragmentary, despite the presence of a fortified village on the heights of Belmonte.
During the dark centuries of the Middle Ages, San Ponso shared the fate of many small towns torn apart by wars, plagued by poverty and epidemics. In the 16th and 17th centuries, it was a hamlet of Salassa and under the jurisdiction of the Counts of Valperga; it regained its civil autonomy with the establishment of the municipality in 1693, only to lose it again in 1929, when it was once more incorporated into Salassa. It became definitively autonomous again in 1947.
Of particular note is the Baptistery, a building dating from the late 10th or early 11th century which was intended to stand alongside a Romanesque parish church, situated where the Baroque parish church dedicated to San Ponso now stands. The site has been home to a cemetery since Roman times, as evidenced by several gravestones from the 1st–2nd centuries AD that have been unearthed. The tall bell tower rising above the dome is a curious addition from 1585, incongruous with the Romanesque style.