Fort Washita was established in 1842 in the Choctaw Nation, Indian Territory, as the southwestern-most military post of the United States. The mission of the soldiers was to protect the recently immigrated Choctaw and Chickasaw Indians. The Southern Plains Indians to the west and non-Indian intruders posed threats to the peace and stability of the region. Troops stationed at Fort Washita on a rotational basis during the 1840s included men belonging to companies from the 2nd Dragoons, U.S. Regiment of Riflemen, and the 6th, 7th, and 5th Infantry Regiments. In the 1850s, soldiers from one battery each of the 2nd and 3rd Artillery were at the fort on frontier duty. From 1858 to the beginning of the Civil War in 1861, elements of the 1st Cavalry and 7th Infantry garrisoned the post.
On May 1, 1861, the fort was abandoned by U.S. forces and occupied the next day by Confederate troops from Texas. Southern soldiers used the post as a headquarters during the remainder of the Civil War. After the war the Chickasaw Nation received the old post grounds and buildings from the federal government. The Colbert family, prominent Chickasaws, owned the property until it was acquired in 1962 by the Oklahoma Historical Society. The site is on the National Register of Historic Places and designated as a National Historic Landmark.