The Washita fort was built in 1842 to house federal troops protecting Choctaw and Chickasaw Indians from raids by plains tribes. It was abandoned in 1861 and taken over by the Confederate Army during the Civil War. According to Wikipedia,
Fort Washita became the headquarters of Brigadier General Douglas Cooper, who assumed command after the battle of Honey Springs. Other Confederate commanders during the Civil War include General Albert Pike, served as commander of Fort Washita for a short time before establishing Fort McCulloch a few miles to the east, and General Stand Watie. Near the end of the war in August 1865 Confederate forces burned the existing buildings and abandoned the post. A confederate cemetery remains to this day on the fort grounds.
After falling into disrepair, the site was purchased and reconstructed in the 1970s by the Oklahoma Historical Society. The site is also known for its ghost legends.