Fort Jefferson Site
Why it's listed
Fort Jefferson was a small frontier fort in what is now Darke County, Ohio, built in the autumn of 1791. After Gen. Harmar's defeat by the Miami in 1790, Territorial Governor Arthur St. Clair marched north from Cincinnati, intending to destroy the Miami villages and build forts along the way. His troops reached this spot on October 13, 1791 and began construction, and by October 24 the garrison could finish the work. The fort was named for Thomas Jefferson. It measured 35 yards square with a bastion at each corner, with barracks and storerooms forming the outer walls. St. Clair left a small force and marched on to disaster on the upper Wabash River. Gen. Anthony Wayne later used the fort as a supply link in his 1793-94 campaign, which led to the Treaty of Greeneville. Nothing of the fort survives today. Markers show the original layout, a fieldstone monument stands on the site, and it has been a state memorial since 1929.
Significance in brief: The fort was built by Gen. Arthur St. Clair's army during the 1791 campaign against the Miami tribes and was named for Secretary of State Thomas Jefferson. Gen. Anthony Wayne later used it as a link in his supply chain during the victorious 1793-94 campaign that led to the Treaty of Greeneville and opened much of Ohio to settlement.
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 70000488, listed November 10, 1970. Summary generated October 2026 (model claude-sonnet-5-5, prompt v1.0-2026-10-29, confidence medium).
Key facts
| Address | OH 121, Fort Jefferson |
|---|---|
| County | Darke County |
| Listed | November 10, 1970 |
| Reference number | 70000488 |
| Resource type | Site |
| Period of significance | 18th Century; specific date 1791 |
| Areas of significance | Military |
| Level of significance | State |
| Status (as stated in the nomination) | Nothing remains of the original fort; markers show the locations of the outer walls, powder magazine and bullock pen, and a fieldstone monument has been erected. The site is a state memorial administered by the Ohio Historical Society. |
| Acreage | 6.5 |
| Coordinates | 40.02543, -84.64557 (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 70000488.
- Nomination form (PDF, National Archives) — catalog entry
- Wikipedia article (used for cross-checking only; text not reproduced here)
- Wikidata Q8564748
- This listing as JSON
Last updated October 2026. Found an error? See the editorial policy for how to report it.