{"nrhp_refnum":"75001514","name":"Johnson Island Civil War Prison and Fort Site","other_names":["Johnson's Island Civil War Prison"],"category":"site","location":{"address":"E shore area of Johnson Island","address_restricted":false,"city":"Danbury","county":"Ottawa County","state":"OH","lat":41.49914268050006,"lon":-82.73088446079633,"geom_source":"nps_gis"},"listed_date":"1975-03-27","is_nhl":true,"nhl_designated_date":"1990-06-21","areas_of_significance":["Historic - Non-Aboriginal","Military"],"significance_levels":["national"],"summary":{"what_it_is":"An archaeological and historic site on Johnson's Island in Sandusky Bay, Lake Erie, in Danbury Township, Ottawa County, Ohio. It was the location of a Union prison for Confederate prisoners and two forts, used from 1862 to 1866.","why_significant":"The island was the site of one of the largest Civil War prisons built in the North, holding over 10,000 Southern soldiers between 1862 and the war's end. It was also the target of rumored and attempted Confederate plots to free prisoners, including the Philo-Parsons incident of 1864. Remains include earthworks of Fort Johnson, artillery emplacements and a Confederate cemetery with 206 graves.","narrative":"Johnson's Island, a 300-acre island in Sandusky Bay about three miles from Sandusky, Ohio, served as a Union prison for Confederate soldiers during the Civil War. Lt. Col. William Hoffman chose it in 1861 because its closeness to Sandusky eased the supply of construction materials and because it was reasonably secure from invasion from Canada. The first prisoners arrived in April 1862, and over 10,000 were held there before the war ended, with about 2,600 present on average. The prison had 13 two-story buildings within a 15-acre enclosure, and two forts were added in 1863 after rumors of raids. Plots to free prisoners, including the 1864 seizure of the steamer Philo-Parsons, came to nothing. Buildings were sold at auction in 1865 and 1866. Today portions of Fort Johnson's earthworks, artillery emplacements and a cemetery with 206 Confederate graves survive, while trees cover most of the former prison grounds.","period_of_significance":"1862-1866","architect_builder":null,"architectural_style":null,"criteria":[],"status_note":"Most prison structures were sold at auction after the war; portions of Fort Johnson's earthworks and artillery emplacements remain, trees cover the former prison area, and the cemetery is in good condition and cared for by the U.S. Government. The island now has summer cottages.","vacant_flag":null,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:53:09.724773-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_OH/75001514.pdf"},"photo":null,"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71990853","wikipedia":"https://en.wikipedia.org/wiki/Johnson_Island_Civil_War_Prison_and_Fort_Site","wikidata":"https://www.wikidata.org/wiki/Q118402956"},"indexable":true,"url":"https://nationalhistoricalregister.com/ohio/ottawa-county/johnson-island-civil-war-prison-and-fort-site-75001514/"}