Dead Confederate soldiers on the Antietam battlefield

The culmination of the Maryland Campaign was the Battle of Antietam, fought on September 17, 1864. This image, captured by Alexander Gardner, features some of the roughly 1,500 Confederate soldiers who died on the bloodiest single day of the Civil War. [Wikimedia Commons]

Maryland Campaign

September 4–September 20, 1862

Also known as the Antietam Campaign, the Maryland Campaign was an ill-fated Confederate attempt to take the American Civil War to Northern soil in 1862. The failure of the invasion provided the impetus for President Abraham Lincoln to issue his Preliminary Emancipation Proclamation.

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Prelude to the Maryland Campaign

Emboldened by the Rebel 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 near Poolesville, Maryland.


Robert E. Lee’s Goals

Beyond Lee’s military goals, economic and political motives prompted 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 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.

  • Lee ordered three columns commanded by Lafayette McLaws, Richard Anderson, and Thomas “Stonewall” Jackson, to march west to capture the federal garrisons to his west at Martinsburg and Harpers Ferry, Virginia (now West Virginia). The two Union garrisons threatened his supply lines through the Shenandoah Valley. Lee determined that he had to eliminate them to avoid the possibility of his army being isolated in Maryland.
  • Lee next ordered a column, commanded by Lieutenant General James Longstreet, to follow Jackson’s men to the vicinity of Hagerstown, Maryland to guard against any potential Union resistance coming south from Pennsylvania.
  • Finally, Lee ordered Major General D.H. Hill to take his command and follow the invasion force up the Hagerstown Road as far as Boonsboro to serve as a rearguard for the army’s stores and artillery.

President Lincoln Turns to McClellan

Meanwhile, sensing the vulnerability of the nation’s capital, President Abraham Lincoln reluctantly turned to Major General George B. McClellan to reinvigorate the Federal forces to 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 armies into a formidable force.

Lee’s Lost Orders

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 next day, members of the 27th Indiana found a copy of Lee’s plans. They 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.

Knowing that Lee had divided his army, McClellan took the initiative and advanced to a position that would prevent the Rebel army from being reunited.

It is unknown when Lee realized that McClellan knew his plans. What is known is Lee’s concern by September 14 that the seizure of Harpers Ferry was taking longer than expected. Lee sent a dispatch urging Jackson and McLaws to finish their task quickly and to rejoin him. When Lee learned that McClellan was marching west from Frederick, he ordered Hill to hold the passes at South Mountain, which separated Lee’s soldiers from the Yankee army.

Battle of South Mountain

On September 14, advance elements of McClellan’s army approached three strategic passes through South Mountain—Crampton’s, Turner’s, and Fox’s Gaps—and fighting erupted. More Union troops moved forward throughout the day and gradually forced Lee to withdraw the stubborn Rebel defenders on September 15. The Union victory at the Battle of South Mountain provided McClellan with an opportunity to crush Lee’s army before it could reunite. Characteristically, McClellan did not take advantage of the Confederates’ precarious situation. While Lee hastened to reassemble his army near Sharpsburg, Maryland, McClellan spent most of the next two days devising plans and deploying troops as they poured through the South Mountain passes.

Rebel Victory at Harpers Ferry

Without the troops delayed at Harpers Ferry, Lee knew that he had little chance of winning an engagement against McClellan’s mounting superior numbers. The Confederate general was considering ending the campaign and returning to Virginia when he received word that the Union garrison at Harpers Ferry had surrendered on September 15. The Confederate victory at the Battle of Harpers Ferry convinced Lee to stand and fight. On September 16, both armies prepared for battle the next day.

The Bloodiest Day of the Civil War

The climactic engagement of the campaign occurred on the morning of September 17, 1862, when the Army of the Potomac and the Army of Northern Virginia met along Antietam Creek, near Sharpsburg. The pitched battle went back and forth the entire day. When the Federals were on the verge of victory, General A. P. Hill and his division arrived on the scene at approximately 4:00 p.m. after a forced march from Harpers Ferry. Hill’s arrival turned the tide and prevented a Confederate defeat. The Battle of Antietam ended as a tactical draw, but it was a strategic Union victory because McClellan halted Lee’s northern advance. The engagement was the bloodiest single-day battle during the American Civil War. McClellan’s army of approximately 75,000 men suffered 12,401 casualties, including 2,108 killed. Lee’s smaller army of approximately 55,000 soldiers suffered 10,316 casualties, including 1,546 killed.

Lee Withdraws

Following a day of truce during which both sides recovered and exchanged their wounded and recovered their dead, Lee began withdrawing his army across the Potomac River at Boteler’s Ford near Shepherdstown, Virginia (present-day West Virginia). Once again, McClellan failed to press the issue.

Battle of Shepherdstown

After crossing the Potomac River, Lee left behind a rearguard of two infantry brigades and forty-five cannons, commanded by Brigadier-General William N. Pendleton, to hold the ford. It was not until late afternoon on September 19 that a detachment of Federal troops from Major General Fitz John Porter’s 5th Corps crossed the river, attacked the Confederate rearguard, and then withdrew. The next morning, Porter sent two divisions back across the river to establish a bridgehead for McClellan’s army.

By that time, Major General A. P. Hill’s “Light Division” had reversed course and marched back towards Shepherdstown in time to counterattack the advancing Bluecoats. When Porter received word that the Confederate force outnumbered his infantry on the Virginia side of the Potomac River, he ordered a withdrawal. The Confederate victory at the Battle of Shepherdstown persuaded McClellan to call off any further pursuit of Lee’s battered army, much to the consternation of President Lincoln and other federal officials. McClellan would later pay for his inertia when Lincoln dismissed him as commander of the Army of the Potomac on November 5, 1862.

Aftermath of the Maryland Campaign

The Battle of Shepherdstown and Lee’s withdrawal from Maryland ended the Maryland Campaign. Although the fighting was over, the campaign precipitated a monumental aftereffect that altered the course of the war. With Lee’s army driven back across the Mason-Dixon Line, President Lincoln, on September 22, 1862, used his constitutional power as commander-in-chief to issue his Preliminary Emancipation Proclamation. The president’s “covenant with God,” which added freeing Southern slaves to the mission of the war, produced major political repercussions, especially in the North, and undoubtedly steeled the resolve to fight on in the South.

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Citation Information

The following information is provided for citations.

  • Article Title Maryland Campaign
  • Coverage September 4–September 20, 1862
  • Author
  • Website Name American History Central
  • Access Date July 27, 2021
  • Publisher R.Squared Communications, LLC
  • Original Published Date
  • Date of Last Update March 17, 2021
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