San Giovanni Incarico is under the the hill of the Guardia and overlooks the valley of the Liri. The name of the village originates from the church dedicated to the saint and the second term comes from the name of one of the downstream areas.
In the district were found remains from the Paleolithic period, and in the valley lie the ruins of a Roman villa and the ancient colony of Fabrateria Nova, founded after the destruction of the nearby Fregellae.
In the Middle Ages, to escape the Saracens, the population took refuge in the hills in a castle under the protection of a nobleman.
The Castle of San Giovanni was founded by Atenolfo II, steward of Aquino, around 949 and its first mention appears in a document of 977 in the archives of the Abbey of Montecassino.
The lords have always been allies of the monks of Monte Cassino, intervening repeatedly in defence of the monastery. After the Norman family of Aquila came the fiefdom of San Giovanni Incarico, followed by the Counts of Poli, French knights along with the Anjou, and the Spinelli.
In 1229 the castle had to surrender to the papal troops and in the following years many from San Giovanni went to the popular Flagella, the Frederick city erected for an anti-papal purpose.
In 1451 the town was granted to the della Rovere, later passed to the Farnese family to whom we owe the statute, and then given to the King of Poland Ladislao VII. Finally it became part of the Neapolitan state in the Bourbon period.
Here many revolutionary activities by brigands took place in the period following the unification of Italy and there was strong emigration.
During World War II, the town was up-turned by the fighting.