The Oklahoma Historical Society operates multiple historic military sites throughout the state. In 1824, Fort Gibson was established to keep peace in frontier Indian Territory. Later in 1824, Fort Towson, near the Red River, guarded the boundary between US territory and Mexico. Fort Washita, established 1842, served to protect the Choctaw and Chickasaw from marauding Plains tribes and non-Indian intruders. Indian Territory's most important battle of the Civil War was fought between Union and Confederate forces on July 17, 1863, at Honey Springs. In 1868, Fort Supply was built as a supply depot for the winter campaign against the Southern Plains tribes. It later served to protect the Cheyenne and Arapaho on their new reservation in western Indian Territory.