{"nrhp_refnum":"70000921","name":"Fort Independence","other_names":["The Castle","Castle William","Castle William &amp","Mary","Fort Mary"],"category":"site","location":{"address":"Castle Island","address_restricted":false,"city":"Boston","county":"Suffolk County","state":"MA","lat":42.338148468500066,"lon":-71.01116871476665,"geom_source":"nps_gis"},"listed_date":"1970-10-15","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Military"],"significance_levels":["national"],"summary":{"what_it_is":"Fort Independence is a pentagonal brick and granite fort on Castle Island in South Boston, Massachusetts. The present structure dates mainly from reconstruction between 1835 and 1851, on a site fortified since 1634.","why_significant":"Castle Island is described as the oldest fortified site in the original Massachusetts Bay Colony, apart from an earlier defense on Fort Hill. It guarded the main ship channel into Boston Harbor and figured in colonial and Revolutionary events such as the 1689 imprisonment of Governor Andros and the quartering of British troops after the Boston Massacre. Its military history lasted 328 years, ending in 1962.","narrative":"Fort Independence occupies Castle Island at the edge of South Boston and guards the main ship channel into Boston Harbor. Fortifications began there in 1634 under John Winthrop, with wooden batteries followed by a castle that burned in 1673. A stone Fort William was completed in 1705 and was regarded as the most impressive fort in British North America. It was renamed Fort Independence in 1798 after Massachusetts ceded it to the United States. John Foncin designed a new five-bastion fort, finished by 1809. Rebuilding began in the 1830s and the brick and granite pentagon was garrisoned again by 1851. The island saw colonial unrest, including the imprisonment of Governor Andros in 1689 and the quartering of British troops after the Boston Massacre, and later Civil War volunteer units. Military use ended in 1962, when the fort returned to the Commonwealth as a historic monument.","period_of_significance":null,"architect_builder":"John Foncin (designer of the early 19th century fort); Colonel William Wolfgang Romer and Capt. John Redknap (Fort William, 1705)","architectural_style":null,"criteria":[],"status_note":"Owned by the Commonwealth of Massachusetts (Metropolitan District Commission), used as a park and historic monument; condition marked as altered and fair.","vacant_flag":null,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:11:55.007854-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/opastorage/live/84/7970/63797084/content/electronic-records/rg-079/NPS_MA/70000921.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/70000921/927310e4a3-800.webp","url_1600":"https://nationalhistoricalregister.com/media/70000921/927310e4a3-1600.webp","licence":"CC BY-SA 4.0","author":"Chris Wood (User:chris_j_wood).","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Fort_Independence_on_Castle_Island.JPG\" rel=\"noopener\">Chris Wood (User:chris_j_wood).</a>, <a href=\"https://creativecommons.org/licenses/by-sa/4.0\" rel=\"license noopener\">CC BY-SA 4.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Fort_Independence_on_Castle_Island.JPG"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/63797084","wikipedia":"https://en.wikipedia.org/wiki/Fort_Independence_(Massachusetts)","wikidata":"https://www.wikidata.org/wiki/Q1438579"},"indexable":true,"url":"https://nationalhistoricalregister.com/massachusetts/suffolk-county/fort-independence-70000921/"}