Colle San Magno is a result of the Barbarian invasions. Before the sixth century the inhabitants of Aquino took refuge on Mount Asprano and at the end of the tenth century, after the invasions, they returned to the valley and created two new towns. One of these is Colle San Magno.
In 994 at the behest of the Abbey of Montecassino citizens left the castle on the mountain to escape the harsh climate and lack of water. Colle San Magno belonged, in order, to the Aquinas, to the Abbey of Montecassino, to the D’Avalos and in 1583 to Boncompagni. In 1796 it became part of the Bourbon Kingdom.