Known since ancient times by the Phoenicians and Greeks, the Romans called it Accipitrum Insula (island of the hawks), due to the presence of the regina falcon. It was colonized in 1738 by a population whose language and origins were Ligurian, from the small Tunisian island of Tabarca. The name of Saint Peter was chosen by the population, out of devotion to the apostle, who, according to legend, had landed there in 46 A.D..
Carloforte, the only inhabited centre and a charming seaside village, is the main town on the island; it has its own special charm and is considered to be, with good reason, one of the most pristine spots in Sardinia and the Mediterranean. It was named in honour of King Carlo Emanuele III. The inhabited center of Carloforte is situated on the eastern shore of the island, where it is less exposed and more protected from the winds.
Going by sea, there are regular ferry connections to the nearby islands of Sant'Antioco and Sardinia. Carloforte's harbour is well equipped for pleasure crafts, and is wide, comfortable and is very well protected.
In January 1793 Carloforte was occupied by French troops, renamed the "Island of Freedom", the mast was raised in the public square and, with the aid of the Pisan revolutionary Filippo Buonarroti, the city's Constitution was written. This short period came to an end in May of the same year, with the Spanish fleet ordering surrender to the French.
The Napoleonic itinerary includes a visit to the town.