Fort Independence (Castle Island) 19th‑century granite fort

Fort Independence, located on Castle Island, is a bastioned granite fortification constructed between 1833 and 1851 to serve as part of Boston Harbor's coastal defenses. The fort contains vaulted casemates that were used as enclosed gun emplacements and magazines during the 19th century. The present stone fort replaced earlier wooden and earthen works on the same site and is preserved as a historic coastal defense structure.