Battle of Crampton ' s Gap The Battle of Crampton ' s Gap ( USA ) or Battle of Burkittsville ( CSA ) was a battle fought between forces under Confederate Brig . Gen . Howell Cobb and Union Maj . Gen . William B . Franklin as part of the Battle of South Mountain on September 14 , 1862 , at Crampton ' s Gap in Western Maryland , during the Maryland Campaign of the American Civil War . Franklin ' s VI Corps attacked a small , hastily assembled Confederate force at Crampton ' s Gap in South Mountain to protect the rear of Maj . Gen . Lafayette McLaws , who was across Pleasant Valley on Maryland Heights taking part in the siege of Harpers Ferry . Despite inferior numbers , the Confederate force held out throughout the day , taking heavy casualties . By the evening the VI Corps broke the Confederate line and proceeded through the gap into Pleasant Valley . Franklin , however , failed to follow up on his success and did not attack McLaws on Maryland Heights . Tactically the battle resulted in a Union victory because they broke the Confederate line and drove through the gap . Strategically , the Confederates were successful in stalling the Union advance and were able to protect McLaws ' rear . Background . On September 13 , 1862 , Union Maj . Gen . George B . McClellan received a lost copy of Robert E . Lee ' s Special Order No . 191 , which detailed the Confederate plan of action in Maryland , including the fact that Lee had divided his army and sent a portion to capture Harpers Ferry . As part of that siege , units under Maj . Gen . Lafayette McLaws were sent to take Maryland Heights and then bombard the Union garrison in the town . To protect his rear flank , McLaws stationed a small guard at Brownsville Gap ( a smaller gap a few miles south of Crampton ' s Gap ) and Crampton ' s Gap , both of which allowed access to Pleasant Valley and the eastern slope of Maryland Heights . The force at Crampton ' s Gap consisted of one battery of artillery , 3 regiments of infantry under Brig . Gen . William Mahone , one brigade under Brig . Gen . Howell Cobb , and a small cavalry detachment under Col . Thomas T . Munford . McClellan ordered Maj . Gen . William Franklin and his VI Corps to set out for Burkittsville from his camp at Buckeystown the following morning at daybreak , with instructions to drive through Crampton ' s Gap and attack McLaws ' rear . Although he sent the order immediately , by allowing Franklin to wait until morning to depart , his order resulted in a delay of nearly 11 hours . Battle . The small Confederate force used the terrain to its maximum advantage with Munford ' s cavalrymen initially stationed at the eastern base of the mountain , the artillery halfway up its slope , and the infantry entrenched at the summit . From their vantage point on the mountain they watched throughout the morning as Franklin ' s VI Corps marched across the Middletown Valley towards them . When the Federals reached Burkittsville around noon , the Confederate artillery opened up . In Burkittsville , while under artillery fire , Franklin assembled his troops into three columns . At 3 p . m . , after a delay of nearly 3 hours , the VI Corps finally began its assault . The reason for the delay has never been ascertained , but it would prove costly . The Union advance was slow and steady , supported by artillery . Their superior numbers quickly overwhelmed the cavalry and artillery on the slopes of the mountain . The retreating Confederates were briefly rallied at the summit by General Cobb , but an oncoming charge by the First New Jersey Brigade ( The first 4 New Jersey regiments ) was too much . Once the VI Corps reached the summit they drove the Confederates from their positions , inflicting heavy casualties , in just 15 minutes of fighting . After the Confederate line at the summit broke , the troops scattered in all direction into Pleasant Valley and were thereafter totally unable give any further fight to the Federals . However , before their rout , they had held out for three hours , which , in concert with the delay of the VI Corps getting to and beginning the attack on Crampton ' s Gap , meant that it was after 6 : 00 p . m . when Franklin reassembled his men in Pleasant Valley and too late to begin a second attack on McLaws ' force on Maryland Heights . The following day Harpers Ferry surrendered to the Confederates , while Franklin sat camped in Pleasant Valley , convinced he was outnumbered by McLaws by nearly two to one . Aftermath . In total , the VI Corps suffered 115 killed , 416 wounded , and 2 missing , for a total of 533 casualties . The Confederate forces suffered 130 killed and 759 wounded , for a total of 887 casualties . Tactically , the Federals were successful in driving the Confederates from the gap , the first time any portion of Lee ' s army had been driven from the field up until this point in the war , and were able to inflict heavy casualties in doing so . Strategically , the Confederate force was able to stall the Federal advance for three hours despite being outnumbered nearly six to one . The delay was long enough to ensure the safety of McLaws on Maryland Heights and capture of Harpers Ferry the following morning . More significantly , after seizing Crampton ' s Gap , General Franklin failed to attack McLaws and allowed Stonewall Jackson ' s Corps to reunite with the main body of the Confederate army at Sharpsburg without a fight , setting the stage for the Battle of Antietam three days later . There Lee hastily stood his ground in the war ' s bloodiest day . President Abraham Lincoln used the marginal Union victory at Antietam as a justification for announcing his Emancipation Proclamation . Preservation . The battlefield and a large area to the east were designated a historic district on the National Register of Historic Places . The Crampton ' s Gap Historic District was designated on January 12 , 2011 , comprising the mountain around Crampton ' s Gap and Brownsville Gap , the town of Burkittsville , and surrounding landscape .