It was founded by the ancient inhabitants of the territory, the Osci, who called it Akere, later changed into Acheruntia. It was a Roman municipium and praefectura, a gastaldat under the Lombards and an important castle throughout the Middle Ages, and from 1059 to 1977 was the Bishopry seat for Basilicata and for centuries also hosted a Seminar. Its diocesis was founded according to some sources by the Saint Peter himself.