Johnson Island Civil War Prison and Fort Site
Also known as: Johnson's Island Civil War Prison
Why it's listed
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.
Significance in brief: 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.
Machine-generated summary. This summary was generated by a language model from the official nomination document and has not been reviewed line by line by an editor. It may contain errors. Check the source document before relying on any detail. Source: nomination document (PDF) · National Archives catalog entry. NRHP reference 75001514, listed March 27, 1975. Summary generated October 2026 (model claude-sonnet-5-5, prompt v1.0-2026-10-29, confidence medium).
Key facts
| Address | E shore area of Johnson Island, Danbury |
|---|---|
| County | Ottawa County |
| Listed | March 27, 1975 |
| Reference number | 75001514 |
| Resource type | Site |
| Period of significance | 1862-1866 |
| Areas of significance | Historic - Non-Aboriginal, Military |
| Level of significance | National |
| National Historic Landmark | Yes, designated June 21, 1990 |
| Status (as stated in the nomination) | 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. |
| Acreage | 300 |
| Coordinates | 41.49914, -82.73088 (NPS GIS) |
What listing means for this property
Sites (archaeological sites, battlefields, landscapes) are often listed with a restricted address to protect them from looting or disturbance. Listing is honorary for private owners; federal undertakings on or near the site go through Section 106 review, and state laws may protect burials and artefacts regardless of listing.
General information, not legal or tax advice. Rules change; confirm with your State Historic Preservation Office or a qualified adviser.
Sources and further reading
- National Park Service, National Register of Historic Places database (snapshot May 2026), reference 75001514.
- Nomination form (PDF, National Archives) — catalog entry
- Wikipedia article (used for cross-checking only; text not reproduced here)
- Wikidata Q118402956
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.