The Battle of South Mountain was fought in Frederick and Washington counties, Maryland, on September 14, 1862, during Confederate General Robert E. Lee's Maryland Campaign.
September 4, 1862: Lee Invades Maryland
Emboldened by the Confederate victory at the Second Battle of Bull Run (August 28 to 30, 1862), Confederate commander Robert E. Lee took the war to Northern soil in the late summer of 1862. On September 4, the Army of Northern Virginia began crossing the Potomac River from west to east near Poolesville, Maryland.
Beyond Lee’s military goals, economic and political motives drove the invasion. The Southern armies needed provisions. Taking the war north would allow Virginia farmers to harvest their crops, unmolested by Union troops. The invasion would also enable Southern troops to commandeer supplies from Northern farmers. Lee also hoped that giving Northerners a taste of war would diminish their resolve, possibly bolstering the prospects of Peace Democrats in the upcoming 1862 Congressional elections. Finally, a victory on Northern soil might induce European powers to lend support to the South.
Lee Divides His Army
Upon entering Maryland, Lee proceeded to Frederick, where he rested his men and met with his generals to devise a campaign plan. By September 9, Lee drafted Special Order Number 191, which outlined his course of action. Assuming that the Federal forces near Washington were still in disarray following their stinging defeat at the Second Battle of Bull Run, Lee believed that it was safe to divide his army temporarily.
- He ordered three columns under the command of Lieutenant General Thomas “Stonewall” Jackson to march west and capture Harpers Ferry, thereby securing his supply lines.
- Lee ordered a column commanded by Lieutenant General James Longstreet to follow Jackson to the vicinity of Hagerstown, Maryland to guard against any Union resistance coming south from Pennsylvania.
- Finally, Lee ordered Major General D. H. Hill’s command to follow the invasion force up the Hagerstown Road as far as Boonsboro and serve as a rearguard for the army’s stores and artillery.
President Lincoln Turns to McClellan
Lee’s assumptions about the Union forces were justified; the federal armies around Washington were in disarray. Sensing the vulnerability of the nation’s capital, President Abraham Lincoln reluctantly turned to Major General George B. McClellan to reinvigorate the federal forces and stop Lee’s advance. On September 2, 1862, Lincoln placed McClellan in command of “the fortifications of Washington, and all the troops for the defense of the capital.” Known for his organizational skills, McClellan merged the Army of Virginia with his Army of the Potomac and quickly transformed the demoralized Union soldiers into a formidable force.
Lee Gets Underway
Lee’s plan got underway on September 10, 1862, when Brigadier General John G. Walker’s Division headed west out of Frederick toward Harpers Ferry. Around noon on September 12, the last of the Confederate troops left Frederick. Only four hours later, advance elements of McClellan’s army marched into Frederick and occupied the same campgrounds that the Rebels had just evacuated.
The Lost Orders
The next day, members of the 27th Indiana found a copy of Lee’s plans. The quickly passed the document up the chain of command where Union officials verified its authenticity. Upon receiving the copy of Lee’s orders, McClellan crowed, “Here is a paper with which, if I cannot whip Bobby Lee, I will be willing to go home.”
McClellan is Emboldened
After becoming privy to Lee’s plans, McClellan became uncharacteristically brisk in his pursuit of the Rebel army. The only major obstacle preventing him from overtaking Lee and defeating Lee’s splintered army was D. H. Hill’s division guarding the passes through South Mountain.
Despite the impression engendered by its name, South Mountain might be more accurately described as a seventy-mile-long range of mountains that separates the Appalachian Plateau from the Piedmont Region in Maryland. South Mountain enters Maryland from Virginia in the southwest and leaves the state at the Pennsylvania border to the northeast. Several passes provide access through the mountain from east to west. Most notable of these are Turner’s Gap to the north, Fox’s Gap in the center (through which the National Road passes), and Crampton’s Gap to the south. Hill stationed troops at each of the gaps to protect Lee as his army moved west from Frederick.
McClellan Reorganizes His Army
As McClellan moved against South Mountain, he temporarily organized his army into three wings.
- The right-wing, commanded by Major General Ambrose Burnside, comprised Major General Joseph Hooker’s 1st Corps and Major General Jesse L. Reno’s 9th Corps. McClellan sent the right Wing to Turner’s Gap and Fox’s Gap in the north.
- The left-wing, commanded by Major General William B. Franklin, comprised his own 6th Corps and Major General Darius N. Couch’s division of the 4th Corps. McClellan sent the left wing to Crampton’s Gap in the south.
- The center-wing, commanded by Major General Edwin V. Sumner, comprised the 2nd Corps and 12th Corps. McClellan held the center-wing in reserve.
September 14, 1862: Clash at South Mountain
Rebels Withstand Federal Assaults at Fox’s Gap
The action at South Mountain began on the morning of Sunday, September 14, when Reno’s men moved against the Confederate defenders at Fox’s Gap, commanded by Brigadier General Samuel Garland. During the early fighting, Union Brigadier General Jacob D. Cox’s Kanawha Division secured much of the land south of the gap, but the Confederates did not crumble. Reinforced by Brigadier General John Bell Hood’s Texas Brigade, the Rebels withstood three spirited Union assaults over the course of the day.
During the brutal fighting, the Confederates mortally wounded Garland and Reno, and they severely wounded future U.S. President Rutherford B. Hayes. Another future U.S. President, William McKinley, also took part in the fighting. Although the Confederate defenders conceded ground, they stubbornly held the pass as the fighting subsided at nightfall.
Rebels Hold at Turner’s Gap
The story at Turner’s Gap was much the same. Late in the afternoon, under Burnside’s directive, Hooker ordered his three divisional commanders, Brigadier General John Hatch, Brigadier General James Ricketts, and Brigadier General George G. Meade, to launch an all-out assault against the Confederate defenders. Meade and Ricketts gained considerable ground on the north side of the gap until being stalled by Brigadier General Robert Rodes’s brigade.
On the south side of the gap, Brigadier General John Gibbon’s brigade led Hatch’s assault. Gibbon’s men performed so superbly that their strike earned them the nickname of the “Iron Brigade.”
Brigadier General Alfred H. Colquitt’s Confederate defenders were equally impressive. Colquitt’s staunch defense earned him the nickname of the “Rock of South Mountain.” Despite their spirited stand, the Yankees gradually drove back the Rebel defenders on both sides of the gap until reinforcements from James Longstreet’s division arrived. When darkness fell, the Confederates still held Turner’s Gap.
Federals Seize Crampton’s Gap
Six miles south of Fox’s Gap, at Crampton’s Gap, events unfolded much more positively for the Federals—but not as favorably as they could or should have. On September 13, McClellan ordered Franklin to seize Crampton’s Gap and then head west to relieve the garrison at Harpers Ferry, which was under siege.
Instead of departing immediately, Franklin moved on the morning of September 14. His troops did not reach Burkittsville, near the mouth of the pass until around noon. Franklin then spent three hours deploying 12,000 Union soldiers to dislodge between 500 to 1,000 Confederate defenders commanded by Colonel William A. Parham.
When the action finally started, the Yankees quickly seized the gap and sent the Rebel defenders scurrying down the western side of the mountain. By the time Franklin rounded up about 400 prisoners and reassembled his forces, it was after 6 p.m. The victorious general determined that it was too late in the day to move west and relieve the Union soldiers who were holding out at Harpers Ferry.
Lee Withdraws Overnight
When the sun set on South Mountain on September 14, 1862, Lee still controlled two of the three passes, if only precariously. Over 51,000 troops had engaged in the fighting that day, some of it brutal hand-to-hand combat. Actual totals differ, but the Confederacy suffered over 3,500 casualties, compared to roughly 2,500 for the Union. With Crampton’s Gap lost and the Rebel defenders barely holding on at Turner’s Gap and Fox’s Gap, Lee ordered Hill to withdraw his troops overnight.
Lee’s withdrawal from South Mountain provided McClellan with an opportunity to get between Longstreet and Jackson and crush Lee’s army before he could reunite it. Characteristically, McClellan did not strike while the iron was hot. While Lee hastened to reassemble his army, McClellan spent most of the next two days devising plans and deploying troops as they poured through the South Mountain passes.
The garrison at Harpers Ferry surrendered to Jackson the day after Franklin belatedly seized Crampton’s Gap. Their surrender enabled Jackson to march east and join Longstreet and Lee near Sharpsburg, Maryland. Encouraged by the reunification of his army, Lee decided to stand and fight rather than retreat to Virginia. With McClellan’s army nearby, however, Lee did not get to fight on ground of his choosing. Instead, the two armies clashed along Antietam Creek on September 17, 1862, in what would be the bloodiest single day of battle during the American Civil War.