Fort Buchanan was a United States Army post founded in 1856 three miles southwest of present-day Sonoita in Santa Cruz County, Arizona on the east slope of what is now called Hog Canyon. At the time, the area was under constant threat from hostile Apaches. Full-scale war with the local Chiricahua Apache was initiated by the Bascom affair in early 1861, during which Lieutenant George Nicholas Bascom and his patrol were based at Fort Buchanan.
The post was officially abandoned in 1861, though troops of the California Column occasionally manned the post during the American Civil War. In February 1865, Apaches attacked and burned the fort in the Battle of Fort Buchanan, forcing the small garrison to retreat. It was then abandoned for good and Fort Crittenden was established half a mile east on the flats in 1867.