In 1865, the United States Army decided that it needed a fort in southeastern Oregon to facilitate the interdiction of Indian raiding parties passing through the area. In 1866, a detachment from Fort Boise was sent to establish the fort. The soldiers arrived on the east side of Warner Valley in late summer. Unable to cross the valley's long chain of lakes and marshes, the soldiers built a winter camp on the east slope of Hart Mountain, overlooking the Catlow Valley. This outpost was called Camp Warner (later known as Old Camp Warner). The camp was sited poorly, and the men had a very difficult winter. In February 1867, General George Crook visited the outpost. Citing the camp's poor location, Crook ordered that the post be moved to the west side of the Warner Valley. When the new camp was finished in July 1867, Old Camp Warner was abandoned. Today, all that remains of Old Camp Warner is two military graves.