Fort Independence (Castle Island) - harbor defense site

Fort Independence on Castle Island in South Boston occupies a site long used for harbor defense, originally known as Castle William in the colonial period. The current stone fort was built in the 19th century on the site of earlier fortifications and guarded approaches to Boston Harbor during multiple conflicts. The location has documented military use dating back to the 17th century and is preserved as a historic fort open to the public seasonally. Interpretive signage at the fort explains its role in Boston's maritime and military history.