{"nrhp_refnum":"70000554","name":"Fort Mifflin","other_names":["Mud Island Fort","Old Fort Mifflin"],"category":"district","location":{"address":"Marina and Penrose Ferry Rds.","address_restricted":false,"city":"Philadelphia","county":"Philadelphia","state":"PA","lat":39.87276768100003,"lon":-75.21462803939292,"geom_source":"nps_gis"},"listed_date":"1970-08-29","is_nhl":true,"nhl_designated_date":"1970-08-29","areas_of_significance":["Military","Engineering"],"significance_levels":["national"],"summary":{"what_it_is":"A group of late eighteenth- and nineteenth-century fortifications and military buildings on Mud Island in the Delaware River at Philadelphia, Pennsylvania, known as Fort Mifflin.","why_significant":"The fort's building phases correspond with major periods of the nation's history, from the 1770s through the twentieth century. Its surviving eighteenth-century stone river wall, its early nineteenth-century buildings and its association with L'Enfant and other French engineers are presented as important both historically and architecturally.","narrative":"Fort Mifflin occupies Mud Island in the Delaware River at Philadelphia, and its buildings were added in several phases from 1772 onward. The surviving stone river wall, laid in the eighteenth century, was regarded as notable for its masonry and for its role in the siege of October-November 1777. The Commandant's House, a pilastered brick building probably begun in 1794, is attributed to Pierre Charles L'Enfant, who worked at the fort in the early 1790s. The 1814 Officers' Quarters has a double gallery facing the parade ground with cast iron grillwork and turned wooden columns. The artillery shed of about 1837 is described as a rare surviving example of its building type. Its engineers included several French officers who had served with Lafayette or emigrated after the Revolution.","period_of_significance":"1772-1900","architect_builder":"Captain John Montresor (chief engineer, first phase); Pierre Charles L'Enfant (1794 phase, probable designer of the Commandant's House)","architectural_style":null,"criteria":[],"status_note":"Described as deteriorated in its condition at the time of nomination.","vacant_flag":null,"machine_generated":true,"model":"claude-haiku-5-5","prompt_version":"v1.1-2026-10-29","generated_at":"2026-10-29 17:12:56.829967-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_PA/70000554.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/70000554/1ae869d799-800.webp","url_1600":"https://nationalhistoricalregister.com/media/70000554/1ae869d799-1600.webp","licence":"CC BY 2.5","author":"Joe Minardi","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Mifflin_Commandant%27s_House03.png\" rel=\"noopener\">Joe Minardi</a>, <a href=\"https://creativecommons.org/licenses/by/2.5\" rel=\"license noopener\">CC BY 2.5</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Mifflin_Commandant%27s_House03.png"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71996924","wikipedia":"https://en.wikipedia.org/wiki/Fort_Mifflin","wikidata":"https://www.wikidata.org/wiki/Q3077947"},"indexable":true,"url":"https://nationalhistoricalregister.com/pennsylvania/philadelphia/fort-mifflin-70000554/"}