Sonnino is a medieval village perched on a hilltop of Colle Sant’Angelo of Monti Lepini. Certainly, the whole area was already inhabited in pre-Roman times by the Volsci as shown by some archaeological finds and history of the surrounding municipalities.
According to legend Sonnino was founded in the VIII century when the inhabitants of Priverno, lower down, took refuge in the hills around a castle to escape the Barbarian invasions and subsequently the Saracens. In fact, the Sonnino name comes from the word ‘top’ to indicate that the town was built on a hill.
With the defeat of the Romans ending maintenance of the water system to the town and the flooding of the plain, the Appian Way was no longer viable for travel for a long stretch.
The first published news of Sonnino dates back to a Papal bull of 999 when Sonnino had already become an important point of refuge for the population. The first lords of Sonnino were the De Sompenino but from 1369 the castle was owned by Onorato I Caetani, and since then there were many families including Gaetani d’Aragona, the Borgias, Carafa and from 1503 the Colonna, who kept it until 1816.