We laid in camp until September 13th¹⁾probably September 11th because the battle was on September 14th., then we marched for three days and went into our first battle, South Mountain, near Sharpsburg, Maryland.  It was one of the hot battles of the war.  Our loss in the regiment was small, but there were over 14,000 dead on the field.  So we were on two fields with over 17,000 dead the first month we were in the war.  It was enough to give some of the boys the “horrors.”

~ Conrad Smith²⁾My Early Life and The Civil War, Conrad Smith, 1920, page 25

Although it has long languished in the shadows cast by Antietam, the September 14, 1862, Battle of South Mountain was in itself a battle of great importance and profound consequence. It was the first major battle fought north of the Potomac and it was there-and not at Antietam-where Lee’s first invasion of Union territory was initially met-and turned back. It was a daylong fight, spread out across many miles of rugged, mountainous terrain, as the two sides slugged it out for control of several key mountain passes. Total casualties exceeded 5,000 men, killed, wounded, or captured, a number comparable to those lost at First Bull Run. By day’s end, George McClellan and his Army of the Potomac emerged triumphant; their first major victory of the war. Conversely, and for the first time since he assumed army command three-and-a-half months earlier, Robert E. Lee suffered a serious battlefield defeat. That night, in ordering a retreat from the mountain, Lee also decided to bring an end to his invasion north. Lee’s retreat took him some eight miles westward across the Antietam Creek where he hoped to regain his lost initiative and score a victory on Union soil. As at South Mountain, however, here again Lee was defeated at the hands of McClellan and his victory-flushed Army of the Potomac.³⁾www.historynet.com

Map of Crampton’s Gap during the Battle of South Mountain, Sept. 14, 1862⁴⁾Library of Congress Map Collections accessed here

On September 14th, 1862, General McClellan ordered Major General William B. Franklin to move the Sixth Corps to Crampton’s Gap, one of three passes over South Mountain that the Union would attack that day.  Franklin’s orders were to take the gap and then proceed south on the western side of the mountain to protect the garrison at Harpers Ferry, about eight miles to the southwest, from McLaw’s two divisions.  Because of Confederate shelling from the gap and a road to the south, Franklin believed he was facing a large rebel force.  In fact, the Confederate defense consisted of only about 1,000 men.  Franklin’s two division totaled 12,3000.  It took several hours to move the Corps to the base of the mountain.  The 139th was in Newton’s brigade in the center of the line.  Colonel Joseph J. Barlett described the charge: “A moment’s consultation with Colonel Torbert decided us to make the charge immediately at a double-quick… the command given to ‘Charge,’ and our whole line advanced with cheers, rushing over the intervening space to the stone wall and routing the enemy.”  After some resistance, the Union soldiers made it through the gap and sent the Confederates pouring down the road… in great disorder.  But Franklin did not complete his orders to stop McLaws.  The garrison at Harpers Ferry was capture and thus set the stage for the September 17th battle at Sharpsburg across the Antietam Creek.⁵⁾Paraphrased from application to the National Register of Historic Places by the Crampton’s Gap Historic District, accessed here.

Crampton’s Gap

Photo and map used by permission and accessed here.