Field Atlas
Battle № 03

Washington County
Maryland

The American Civil War · Eastern Theater

ANTIETAM

For twelve hours, two armies fought across farms and creek crossings near Sharpsburg. About 23,000 soldiers were killed, wounded, or missing—the bloodiest single day in American history.

17 SEP 1862
Union and Confederate infantry fighting across an open field in Thure de Thulstrup's Battle of Antietam
Battle of Antietam, Thure de Thulstrup, 1887 Library of Congress
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September, 1862

Lee crossed the Potomac.
McClellan followed west.

After victory at Second Manassas, General Robert E. Lee carried the Army of Northern Virginia into Maryland. He hoped to move the war beyond Virginia, gather supplies, influence Northern politics, and perhaps encourage foreign recognition of the Confederacy. 1

The divided army

Lee split his army to secure his supply line and capture the United States garrison at Harpers Ferry. The maneuver created opportunity—and exposed each separated command to defeat. 2

Frederick South Mountain Sharpsburg

The campaign road west

Before the first shot

Lee’s plan fell into Union hands.

On September 9, Lee issued Special Orders No. 191, directing his scattered columns through western Maryland. A copy intended for Major General D. H. Hill was lost. Four days later, soldiers of the 27th Indiana found it near Frederick inside an envelope with two cigars. 2

The document reached Major General George B. McClellan, commander of the Union Army of the Potomac, by noon. He now knew the broad shape of Lee’s campaign and ordered his army forward. Fighting at South Mountain on September 14 forced Confederate defenders from the passes, but the delay allowed Lee’s separated columns to begin reuniting. 2

After Harpers Ferry surrendered on September 15, Lee chose to make a stand west of Antietam Creek. His right rested near the Potomac River and his left extended north of Sharpsburg. With only one practical route of retreat behind him, Lee faced a larger Union army gathering across the creek. 1

Wednesday, September 17

The first attack crossed
the Cornfield at dawn.

≈ 5:30 A.M.

01 / The bloodiest day

Twelve hours

WED
SEP 17

The Cornfield

Hooker struck Lee’s left

Major General Joseph Hooker’s I Corps advanced south through mist and tall corn toward the Dunker Church. Confederate infantry under Thomas “Stonewall” Jackson met them with artillery and musket fire.

Attacks and counterattacks swept across the Miller farm. Units entered the corn in line and came out shattered. For nearly four hours, about 27,000 men fought in and around the Cornfield; the National Park Service estimates roughly 8,200 casualties there. 3

The 24-acre Cornfield changed hands repeatedly before the northern phase of the battle subsided.

West Woods

Sedgwick’s division was broken

Major General Edwin Sumner sent John Sedgwick’s division into the West Woods in three long lines. The formation pushed beyond support on its flanks and ran into Confederate infantry and artillery converging from several directions.

The Federal advance collapsed in about twenty minutes. More than 2,200 of Sedgwick’s 5,300 men were killed or wounded. The reverse ended the strongest Union effort against Lee’s left. 3

The Sunken Road

The Confederate center bent

A farm lane worn below the surrounding fields became a ready breastwork for Confederate infantry. Wave after wave of Union troops crossed the Roulette and Mumma farms toward the road.

For about three hours, a few thousand Confederates held off nearly 10,000 Federals. A misunderstood order finally opened a gap and Union fire swept the lane from its flank. The defenders withdrew, leaving the road so filled with bodies that it became known as Bloody Lane. 3

Lower Bridge

Burnside crossed Antietam Creek

On the Union left, Major General Ambrose Burnside’s IX Corps struggled to cross a narrow stone bridge beneath a steep bluff. Roughly 500 Georgians used the high ground to delay a force many times their size for three hours.

Union troops finally seized the crossing around 1:00 p.m. Burnside then needed time to move thousands of men over the creek and reform. The bridge would thereafter bear his name. 1

Nearby fords existed, but steep banks, imperfect maps, and resistance made every crossing difficult.

South of Sharpsburg

A. P. Hill stopped the final attack

Burnside’s troops advanced toward Sharpsburg and began to turn Lee’s right. At the critical moment, Major General A. P. Hill’s division arrived after a forced march from Harpers Ferry.

Hill struck the exposed Union flank and drove it back toward Antietam Creek. Darkness ended the fighting. McClellan had committed his army in separate blows rather than one sustained attack, while Lee had shifted nearly every available unit to meet each crisis. 1

How Antietam was seen

The dead had not yet been buried.

Two days after the battle, photographer Alexander Gardner and his assistant James Gibson reached Antietam with a wagon darkroom, glass plates, and chemicals. They made about seventy photographs before the dead had been removed from the field. 4

Earlier war photography had largely shown camps, fortifications, and posed soldiers. Gardner’s Antietam plates showed bodies along the Hagerstown Pike, at the Dunker Church, and in the Sunken Road. Stereographs gave viewers an unsettling illusion of depth.

Mathew Brady displayed the photographs at his New York gallery. Newspapers could not yet reproduce a photograph directly, but woodcuts carried versions of the images across the country. For many civilians, Antietam made the physical cost of the war newly immediate. 4

After the firing

Lee’s army still held its line.

The guns fell silent, but thousands of wounded soldiers remained between and behind the lines. Lee’s battered army stayed west of Antietam Creek through September 18, daring another attack. McClellan did not make one. Both commanders gathered the scattered remains of their armies while burial parties and medical details moved over the field. 1

The battle was tactically inconclusive. The campaign was not.

Lee’s invasion of Maryland had been stopped.

One day 23,000 killed, wounded, or missing

02 / The withdrawal

Across the Potomac

THU
SEP 18

The day after

Neither commander renewed the battle.

Lee’s army had survived five major Union attacks, but its losses and position made another offensive impractical. Federal artillery dominated the ground across which a Confederate counterattack would have to move.

McClellan’s Army of the Potomac still outnumbered Lee, and he had kept substantial forces in reserve during the battle. Yet the scale of the casualties, uncertainty about Lee’s strength, and the disruption of his own commands made McClellan unwilling to attack again. 1

87,000

Union army

41,000

Confederate army

After nightfall

Lee withdrew into Virginia

On the night of September 18–19, Confederate columns crossed the Potomac at Boteler’s Ford near Shepherdstown. Artillery and a rear guard covered the movement until the army was safely on the Virginia side.

Union troops probed across the river on September 19 and 20 but were driven back. McClellan did not mount a sustained pursuit. Lee’s army remained dangerous, but its first invasion of the North was over. 1

The ledger

About 23,000 men fell
in twelve hours.

Exact figures vary. The National Park Service notes that the catastrophic losses made a perfect count impossible. Casualties include soldiers killed, wounded, missing, or captured. 6

Army Killed Wounded Missing Total
Union 2,108 9,549 753 12,410
Confederate ≈ 1,550 ≈ 7,750 ≈ 1,020 ≈ 10,320

No other single day in American history produced so many battle casualties.

Antietam National Battlefield 6

After Antietam

A battlefield check became a political turning point.

Antietam did not destroy Lee’s army, and McClellan’s refusal to pursue disappointed Abraham Lincoln. But Lee had withdrawn from Union territory. That result gave the administration the success it needed to announce a profound change in the war’s purpose. 5

On September 22, five days after the battle, Lincoln issued the preliminary Emancipation Proclamation. It warned that enslaved people in states still rebelling on January 1, 1863, would be declared “then, thenceforward, and forever free.” The final proclamation transformed emancipation into an explicit Union war aim. 5

The proclamation did not free enslaved people in loyal border states such as Maryland, where the battle had been fought. Its reach depended on Union military power. Even so, it linked victory with freedom, discouraged European support for the Confederacy, and opened the United States armed forces to Black men. 5

01

The invasion ended

Lee returned to Virginia without the supplies, political impact, or decisive victory his Maryland Campaign had sought.

02

Emancipation became a war aim

Lincoln used the campaign’s outcome to announce the preliminary Emancipation Proclamation and redefine what Union victory would mean.

03

McClellan lost command

Lincoln removed McClellan in November after weeks of delay. Antietam had stopped Lee, but it had not produced the pursuit the president demanded.

Sources & notes

Sources for this account.

The narrative draws primarily on National Park Service battlefield interpretation and Library of Congress collection records. Numbered references in the text point to the notes below.

  1. National Park Service, “Antietam: Lead Up to and After.”

    Strategic setting, troop strengths, sequence of the battle, Lee’s decision to hold on September 18, and the withdrawal across the Potomac.

  2. National Park Service, “Special Orders No. 191.”

    Lee’s divided campaign plan, discovery of the lost copy, and McClellan’s response before South Mountain and Antietam.

  3. Antietam National Battlefield, “Driving Tour.”

    Fighting in the Cornfield, West Woods, Sunken Road, Lower Bridge, and the final attack.

  4. Antietam National Battlefield, “Photography at Antietam.”

    Gardner and Gibson’s work on the battlefield, stereographs, Brady’s New York exhibition, and the images’ public impact.

  5. National Park Service, “What Comes Out of Antietam.”

    The preliminary Emancipation Proclamation, its relationship to the campaign, and its military, diplomatic, and political consequences.

  6. Antietam National Battlefield, “Casualties.”

    Approximate killed, wounded, missing, and total losses by army, together with the park’s caution that exact figures are impossible to compile.