South Mountain
a ridge of the Alleghanies, near Middletown, Frederick co., Md.; the scene of a battle, Sept. 14, 1862, between the Union troops, under General Reno, composed of Reno's and Hooker's corps of General McClellan's army, and the Confederates, about 30,000 strong, under Generals Hill and Longstreet, in which, after a desperate struggle continuing throughout the day, the Union forces were victorious. General Reno was killed in the action. a