Through the territory of Santopadre ran the ancient Via Latina that connected Arpino with Aquino and Cassino and where the remains of Roman villas were found along with funerary and sacred items. The Romans buried their dead in the streets. Probably, Santopadre began just as a resting place for shepherds and travellers.
In the seventh century Folco came, one of the English saints linked to southern Lazio and a miracle worker during the plague epidemics.
In a document of the tenth century there appears the phrase ‘castrum Foroli’ which implies that a castle had already been built with defensive walls in the village of Foruli (original name of Santopadre).
From 1201 the name of Santopadre appears in documents and in the registries of tithes (Rationes Decimarum) of 1308 and 1325 these referrals are incorporated by reference to the castrum of Santo Padre (or San Pietro).
The castle was first subject to control by the Lombard feudal lords before passing under the control of the Papal States. In 1215 it was ruled for six years by Riccardo Conti, brother of Pope Innocent III.
Santopadre later entered the Duchy of Sora in the domain of the Cantelmos family, then Aldo de’Conti, Lord of Valmontone. In 1472 it passed to the Della Rovere family thanks to Pope Sixtus IV Della Rovere.
In 1494, in the struggle between the Angevin Charles VIII and Ferdinand II of Aragon, the Marquis of Pescara Alfonso Davalos was stripped of the County of Arpino in favour of Giovanni della Rovere, Duke of Sora and Arce, but the following year, as soon as Charles VIII had departed, the partisans of the Aragonese rose again.
In 1683 Santopadre and the Duchy of Sora were purchased by the Boncompagni family who kept it until 1796. The name refers to the Patron San Folco, called the Holy Father for the miraculous events that were attributed after his death.
From 1796 it entered the Kingdom of the Bourbons of Naples until Italian unification.