San Antonio is also the hub of the fishing area that stretches along the Chilean coast from Rocas de Santo Domingo to Cartagena.

It is located at 33°35′S and 71°37′W and borders Cartagena to the north, Melipilla and the Maipo River to the east, Santo Domingo and San Pedro to the south, and the Pacific Ocean to the west.

[1] As a commune, San Antonio is a third-level administrative division of Chile administered by a communal council, headed by an alcalde who is directly elected every four years.

The 2008-2012 alcalde is Omar Vera Castro, who is advised by six councilors: Within the electoral divisions of Chile, San Antonio is represented in the Chamber of Deputies by María José Hoffmann (UDI) and Víctor Torres (PDC) as part of the 15th electoral district, (together with Santo Domingo, Cartagena, El Tabo, El Quisco, Algarrobo and Casablanca).

Another attraction is the Municipal Museum of Natural Sciences and Archaeology of San Antonio, with its collections principally dedicated to the natives that lived in the zone of the central sea of Chile, and the wildlife in the area.

This museum contains huge skeletons of sea mammals, among those is the blue whale, a garden with natural species, aquariums, and the rescue and rehabilitation center of wild fauna.