Admission to Fort Jefferson is free.
- Open daily during daylight hours
- Location: (Map It) Fort Jefferson, Ohio near Greenville, Ohio at County Road 24 and State Route 121
- Phone: 937-547-7370 or 800-686-1535
Fort Jefferson is in Fort Jefferson, Ohio near Greenville, Ohio. Built in 1791, this fort served as an outpost to General Arthur St. Clair. Its purpose was to shelter army supplies and guard against area Indians. It was abandoned in 1796 and is now a park with a monument, twenty-feet high, marking the site where it once stood. Nothing of the fort remains here.