Vallemaio was founded in the Middle Ages by the dukes of Gaeta and is mentioned for the first time in 1040 in the records of the Abbey of Montecassino. It was subject to the control of the Abbey and in 1421, at the behest of Pope Martin V, was devastated. In 1487 it passed permanently under the jurisdiction of the Kingdom of Naples. The historical and architectural heritage were damaged by bombing during the second world war.
Until 1932 it was called Vallefredda, for the harsh winter weather, and changed its name to remind all that it lies at the foot of Mount Maio.