American Civil War: Battle of South Mountain

Major General George B. McClellan. Photograph Courtesy of the National Archives & Records Administration

Battle of South Mountain - Conflict:

The Battle of South Mountain was part of the 1862 Maryland Campaign during the American Civil War.

Battle of South Mountain - Date:

Union forces attacked the gaps on September 14, 1862.

Armies & Commanders:



Battle of South Mountain - Background:

In September 1862, Confederate General Robert E. Lee began moving his Army of Northern Virginia north into Maryland with the goal of severing the rail lines to Washington and securing supplies for his men. Dividing his army, he sent Major General Thomas "Stonewall" Jackson to capture Harper's Ferry, while Major General James Longstreet occupied Hagerstown. Pursuing Lee north, Union Major General George B. McClellan was alerted on September 13, that a copy of Lee's plans had been found by soldiers from the 27th Indiana Infantry.

Known as Special Order 191, the document was found in an envelope with three cigars wrapped in a piece of paper near a campsite recently used by Major General Daniel H. Hill's Confederate division. Reading the orders, McClellan learned Lee's marching routes and that the Confederates were spread out. Moving with uncharacteristic speed, McClellan began putting his troops in motion with the goal of defeating the Confederates before they could unite. To expedite passing over South Mountain, the Union commander divided his force into three wings.

Battle of South Mountain - Crampton's Gap:

The Left Wing, led by Major General William B. Frankin was assigned to capture Crampton's Gap. Moving through Burkittsville, MD, Franklin began deploying his corps near the base of South Mountain early on September 14. At the eastern base of the gap, Colonel William A. Parham commanded the Confederate defense which consisted of 500 men behind a low stone wall. After three hours of preparations, Franklin advanced and easily overwhelmed the defenders. In the fighting, 400 Confederates were captured, most of who were part of a reinforcement column sent to aid Parham.

Battle of South Mountain - Turner's & Fox's Gaps:

To the north, the defense of Turner's and Fox's Gaps was tasked to the 5,000 men of Major General Daniel H. Hill's division. Spread over a two mile front, they faced the Right Wing of the Army of the Potomac led by Major General Ambrose Burnside. Around 9:00 AM, Burnside ordered Major General Jesse Reno's IX Corps to attack Fox's Gap. Led by the Kanawha Division, this assault secured much of land south of the gap. Pressing the attack, Reno's men were able to drive Confederate troops from a stone wall along the crest of the ridge.

Exhausted from their efforts, they failed to follow up this success and the Confederates formed a new defense near the Daniel Wise farm. This position was reinforced when Brigadier General John Bell Hood's Texas Brigade arrived. Re-commencing the attack, Reno was unable to take the farm and was killed in the fighting. To the north at Turner's Gap, Burnside sent Brigadier General John Gibbon's Iron Brigade up the National Road to attack Colonel Alfred H. Colquitt's Confederate brigade. Overrunning the Confederates, Gibbon's men drove them back up into the gap.

Widening the assault, Burnside had Major General Joseph Hooker commit the bulk of I Corps to the attack. Pressing forward, they were able to drive the Confederates back, but were prevented from taking the gap by the arrival of enemy reinforcements, failing daylight, and rough terrain. As night fell, Lee assessed his situation. With Crampton's Gap lost and his defensive line stretched to the breaking point, he elected to withdraw west in an effort to reconcentrate his army.

Aftermath of the Battle of South Mountain:

In the fighting at South Mountain, McClellan suffered 443 killed, 1,807 wounded, and 75 missing. Fighting on the defensive, Confederate losses were lighter and numbered 325 killed, 1560 wounded, and 800 missing. Having taken the gaps, McClellan was in prime position to achieve his goal of attacking the elements of Lee's army before they could unite. Unfortunately, McClellan reverted to the slow, cautious behavior which had been the hallmark of his failed Peninsula Campaign. Lingering on September 15, he provided time for Lee to reconcentrate the bulk of his army behind Antietam Creek. Finally moving forward, McClellan engaged Lee two days later at the Battle of Antietam.

Despite McClellan's failure to capitalize on the capture of the gaps, the victory at South Mountain provided a much needed victory for the Army of the Potomac and helped to improve morale after a summer of failures. Also, the engagement ended Lee's hopes for staging a prolonged campaign on Northern soil and put him on the defensive. Forced into making a bloody stand at Antietam, Lee and the Army of Northern Virginia were compelled to retreat back to Virginia after the battle.

Selected Sources