{"nrhp_refnum":"70000426","name":"Fort Ontario","other_names":["Fort Ontario Military Reservation"],"category":"district","location":{"address":"1 E 4th St.","address_restricted":false,"city":"Oswego","county":"Oswego County","state":"NY","lat":43.46534148150005,"lon":-76.5082838425111,"geom_source":"nps_gis"},"listed_date":"1970-12-18","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Military","Social History"],"significance_levels":["national"],"summary":{"what_it_is":"Fort Ontario is a pentagonal stone military fort at East 7th Street and Lake Ontario in Oswego, New York. The present fort's walls date from 1860, and it is the third fort on the site, begun in 1839.","why_significant":"The nomination cites nearly two hundred years of active military service, from the first British fort of 1755 through the Revolutionary War, the War of 1812, the Civil War era and both World Wars. The site is significant in military history. After the Army abandoned it in 1946, it became an historical museum property.","narrative":"Fort Ontario is a pentagonal stone fortification on the shore of Lake Ontario in Oswego, New York. Five arrow-shaped bastions mark its corners, and an irregular oval courtyard holds the powder magazine, officers' quarters and post headquarters. The cut-stone walls date from 1860, while the interior buildings are stone, wood and brick. The powder magazine was built between 1839 and 1844, and the west artillery casemate holds a battery of 24 and 32 pound howitzers. The site has hosted three forts. The British built the first in 1755 to challenge the French, and it was destroyed in 1756. A stronger second fort followed in 1759, was used in the Revolutionary War and the War of 1812, and was captured and destroyed in 1814. The third fort began in 1839 during tensions over Canada's Patriot War and was upgraded in 1860. It later served as a training post, a World War I hospital camp and a World War II training installation. The Army left in 1946, and the fort became a museum property.","period_of_significance":null,"architect_builder":null,"architectural_style":null,"criteria":[],"status_note":"State-owned, in good condition, occupied and open to the public during specified hours as an historical museum; abandoned by the Army in 1946.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:50:39.725337-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_NY/70000426.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/70000426/1c1ebdfea7-800.webp","url_1600":"https://nationalhistoricalregister.com/media/70000426/1c1ebdfea7-1600.webp","licence":"CC BY-SA 3.0","author":"Ad Meskens","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Fort_Ontario_5.jpg\" rel=\"noopener\">Ad Meskens</a>, <a href=\"https://creativecommons.org/licenses/by-sa/3.0\" rel=\"license noopener\">CC BY-SA 3.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Fort_Ontario_5.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/75320829","wikipedia":"https://en.wikipedia.org/wiki/Fort_Ontario","wikidata":"https://www.wikidata.org/wiki/Q3077968"},"indexable":true,"url":"https://nationalhistoricalregister.com/new-york/oswego-county/fort-ontario-70000426/"}