The Battle of South Mountain—known in several early Southern accounts as the Battle of Boonsboro Gap—was fought September 14, 1862, as part of the Maryland Campaign of the American Civil War. Three pitched battles were fought for possession of three South Mountain passes: Crampton's, Turner's, and Fox's Gaps. Maj. Gen. George B. McClellan, commanding the Union Army of the Potomac, needed to pass through these gaps in his pursuit of Confederate General Robert E. Lee's precariously divided Army of Northern Virginia.