Fort Gadsden, Military fort in Franklin County, United States.

Fort Gadsden is the later of two forts whose ruins lie at Prospect Bluff Historic Sites, on a 12-foot bluff above a bend of the Apalachicola River in Franklin County, about 6 miles southwest of Sumatra. The 1818 fort was built inside the walls of the earlier Negro Fort, destroyed by a magazine explosion in 1816. The photograph shows an open grassy field with bare soil patches, a line of oaks and a thin pole, with water beyond the trees.

Lieutenant Colonel Edward Nicolls of the Royal Marines built the first fort at Prospect Bluff in 1814, during the War of 1812, arming it with cannon and munitions. When the British left Florida in spring 1815 they handed it, fully armed, to about 300 fugitive slaves, 30 Seminoles and Choctaw, and it became known as Negro Fort. A heated cannonball from U.S. forces blew up its powder magazine on 27 July 1816. In 1818 Fort Gadsden was built within the former walls.

After the British left in 1815, about 300 fugitive slaves, 30 Seminoles and Choctaws, and disbanded Colonial Marines held the fort; word of the "Negro Fort" drew some 800 more runaways to the surrounding area. Led by a Black man named Garson and a Choctaw chief, its inhabitants raided across the Georgia border, and the Savannah Journal warned that the settlement tempted slaves to insubordination.

The site lies on the Apalachicola River, 6 miles southwest of Sumatra, Florida, and is reached by road through the Apalachicola National Forest; it is 198 miles from Pensacola and 271 miles from St. Augustine. There is no museum building: interpretive signage, a picnic pavilion and rest rooms stand on the grounds. The photograph shows an open grassy field with a line of oaks and the river beyond, so the fort earthworks are not visible from this spot.

The site preserves archaeological evidence showing how British soldiers, Native Americans, and African people interacted during this period of territorial conflict and change. These layers of history remain visible in the different remains and artifacts that have been uncovered across the grounds.