The Battle of Antietam — Bloodiest Day of the Civil War

September 17, 1862 — or The Battle of Sharpsburg

The Battle of Antietam took place on September 17, 1862. It is one of the most famous battles of the war, and was the single bloodiest day, as both sides suffered an estimated 23,000 casualties. The battle ended in a draw, however the Union gained a tactical victory.

Robert E Lee, 1864, Portrait

The Battle of Antietam ended Lee’s first invasion of the North. Image Source: Wikipedia.

Battle of Antietam Summary

The Battle of Antietam — also known as the Battle of Sharpsburg — occurred in 1862 when Confederate General Robert E. Lee led his army into Maryland. By invading the North, he hoped to obtain provisions and possibly gain European support. Union General George McClellan was tasked with stopping Lee’s advance, and after receiving a copy of Lee’s Special Order, No. 191, he advanced to prevent the Confederate army from reuniting. The two armies clashed on September 17, resulting in the bloodiest single day of the Civil War, with over 23,000 casualties. Although neither side achieved a clear victory, the Union was able to stop Lee’s campaign, and President Lincoln used the event as an opportunity to issue the Preliminary Emancipation Proclamation.

Battle of Antietam, Illustration, Kurz and Allison
Battle of Antietam. Image Source: Library of Congress.

Events Leading to the Battle of Antietam

Emboldened by the Confederate victory at the Second Battle of Bull Run (aka the Second Battle of Manassas) (August 28–30, 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 and entered 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 also would enable Southern troops to commandeer supplies from Northern farmers. Lee also hoped that giving Northerners a taste of war would diminish their resolve. Finally, a victory on Northern soil might induce European powers to lend support to the South.

Upon entering Maryland, Lee proceeded to Frederick, where he split his army into four major attack groups. Lee assumed that the Union forces, still in disarray from the stinging defeat at Bull Run, could not move from Washington, D.C., in time to endanger his divided army.

Meanwhile, alarmed by the vulnerability of the nation’s capital, U.S. President Abraham Lincoln turned to Major General George McClellan to reinvigorate the Federal forces to stop Lee’s advance. Known for his organizational skills, McClellan quickly rebuilt his demoralized Army of the Potomac into a formidable force.

George McClellan, Portrait, Brady
General George McClellan (USA). Image Source: Wikipedia.

Fortune smiled upon the Federal cause on September 13, 1862, when Union soldiers found a misplaced copy of Lee’s Special Order, No. 191 wrapped around some cigars. Federal soldiers quickly passed the orders up the chain of command to McClellan.

Realizing the importance of the document, the jubilant Union commander exclaimed to Brigadier General John Gibbon, “Now I know what to do! 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 determined to take the initiative and advance to a position that would prevent the Confederate Army from reuniting before he could defeat it.

Suspecting McClellan’s intentions, Lee slowed the Union Army’s advance through the passes of South Mountain while the Army of Northern Virginia reunited. When McClellan arrived near Sharpsburg, in central Maryland, on September 16, he discovered Lee had established a battle line west of Antietam Creek, stretching along Hagerstown Turnpike for roughly 2.5 miles. The northern end of the line started about two miles north of Sharpsburg; the southern end of the line ended about one-half mile below the small town.

As McClellan’s army prepared to bivouac for the evening, McClellan drafted a straightforward battle plan. The next day, his army would strike at each of Lee’s flanks simultaneously, followed by a massive assault on the Confederate center.

Morning Assault at the Cornfield

Major General Joseph Hooker’s 1st Corps and Major General Joseph K. Mansfield’s 12th Corps spent the night of September 16 camped north and west of Lee’s right flank in an area known as the North Woods. As daylight broke the next morning, roughly 16,000 Union soldiers prepared to advance against Lee’s left flank. West of them, Captain John Pelham’s Battery on Nicodemus Heights touched off the battle by launching an artillery barrage against them.

Joseph Hooker, Civil War General
General Joseph Hooker (USA). Image Source: Library of Congress.

At about the same time, Brigadier General Truman Seymour’s Brigade (3rd Division, 1st Corps) skirmished with a Confederate brigade commanded by Colonel James A. Walker near an area known as the East Woods, located south and east of Hooker. When Hooker heard the firing near the East Woods, he ordered his troops forward.

By 6 a.m., marching south, the vanguard of the Federal assault on Lee’s left flank approached a twenty-four-acre cornfield south of the North Woods. As the Yankees left the woods they came under artillery fire from Pelham’s Battery to their west and from Colonel Stephen D. Lee’s Battalion near the Dunker Church to their south.

Battle of Antietam, Dunker Church, Gardner
Photograph of the Dunker Church at Antietam. Image Source: Library of Congress.

Pressing on through the morning fog, the Yankees crossed a plowed field and then a grass field before scaling a wooden fence and entering a field of head-high corn. Roughly 200 yards to their front, Brigadier General Alexander Lawton’s Brigade (Richard Ewell’s Division, Thomas Jackson’s Wing), commanded by Colonel Marcellus Douglass, was lying in wait with their muskets trained on the edge of the cornfield.

When the Federals emerged from the rows of corn, the Confederates greeted them with a volley of hot lead that touched off a monumental struggle. After nearly four hours of brutal combat involving thousands of soldiers, possession of the Cornfield changed hands at least six times with no clear victor.

Some units suffered terribly during the clash. On the Confederate side, the 1st Texas Regiment lost 186 of its 211 men. The 6th Georgia Regiment lost 198 of its 250 men. Nearly sixty percent of the Confederate soldiers in Brigadier General John Bell Hood’s Division of Major General James Longstreet’s Left Wing were killed or wounded.

Battle of Antietam, 1862, Union Troops Crossing Antietam Creek
Union troops crossing Antietam Creek. Image Source: Frank Leslie’s Scenes and Portraits of the Civil War, 1894.

West Woods

When the fighting at the Cornfield took a turn for the worse for the Union, at 7:20 a.m., General McClellan ordered Major General Edwin V. Sumner‘s 2nd Corps to cross Antietam Creek and enter the fray.

At roughly 9:15 a.m., the 5,200 soldiers of Major General John Sedgwick’s 2nd Division streamed out of the woods on the east side of the Cornfield (East Woods). Upon meeting no resistance, they crossed the Hagerstown Pike and entered the woods on the west side (West Woods).

As the vanguard of Sedgwick’s troops moved through the West Woods, Major General Lafayette McLaws’ Division joined Brigadier General Jubal A. Early‘s Brigade in a flank attack that surprised the Yankees. In just twenty-five minutes the 15th Massachusetts Regiment lost over 360 of its 600 soldiers. By the time the melee ended about 10:30 a.m., the Confederates had killed or injured 2,200 of the 5,200 Federal soldiers who entered the West Woods.

Confederate pursuit of the fleeing Federals brought an end to the morning’s action on the north end of the battlefield. By the time the fighting waned, at about 10 a.m., roughly 10,000 soldiers had perished or been wounded. The engagements in and around the Cornfield and the West Woods framed the deadliest chapter of the bloodiest single day of combat during the Civil War, but the fighting was far from finished.

The Sunken Road

At roughly the same time that the Confederates struck Sedgwick’s exposed flanks in the West Woods, Brigadier General William French’s 3rd Division (2nd Corps) launched an attack against Confederates occupying the Sunken Road—an old wagon route that connected to the Hagerstown Turnpike near the center of Lee’s line. Years of erosion and use had transformed the road into a long swale, creating an ideal defensive position for the roughly 2,200 Confederate soldiers from D.H. Hill‘s Division (Jackson’s Left Wing) stationed there.

French’s initial assault began around 9:30 a.m. An hour later, Major General Israel Richardson’s 1st Division (2nd Corps) joined the action. The two sides slugged it out until about noon when the Federals forced the Confederates to retreat southward. As the Yankees followed in hot pursuit, a Confederate shell mortally wounded Richardson causing the Union command structure to falter. The Confederates rallied and drove the Federals back across the Sunken Road.

During the three-and-one-half hours of fighting along the Sunken Road, another 5,500 men were killed or wounded, bringing the total number of casualties up to over 16,000. The large number of soldiers killed and wounded at the Sunken Road would later cause it to be remembered as the Bloody Lane.

Burnside Bridge

While Union troops were advancing against the right end of the Confederate line at the Cornfield and the West Woods, Major General Ambrose Burnside searched for a way to get his 9th Corps across Antietam Creek to assault Lee’s left flank on the southern end of the battlefield. Because the water in the stream was chest-deep, Burnside found only two options—the Lower Bridge (also known as the Rohrbach Bridge) and Snavely’s Ford about two-thirds of a mile downstream.

Battle of Antietam, Burnside Bridge, Photograph
Burnside Bridge. Image Source: National Park Service.

Atop the ridgeline on the west side of the stream, roughly 500 Confederate soldiers commanded by Brigadier General Robert Toombs guarded the crossings. Stretched in a line approximately two-thirds-of-a-mile-long along high ground overlooking the creek, the Confederate defenders had an excellent field of fire.

At about 9:30 a.m., Burnside attempted to get his corps across the twelve-foot-wide bridge. Two early attempts to reach the bridge under heavy Confederate fire failed. During a third try at about 1 p.m., 700 soldiers from Brigadier General Edward Ferrero’s 2nd Brigade (2nd Division, 9th Corps) reached the mouth of the bridge and fanned out behind a wooden fence to the south and a stone wall to the north. Following a three-hour clash, the Federals prevailed, and the Confederates withdrew to their lines south of Sharpsburg. When the Confederate defenders at Snavely’s Ford, under pressure from General Isaac P. Rodman’s 3rd Division of 3,000 Federals, learned that Ferrero’s soldiers had crossed the bridge, they also abandoned their position.

After carrying the bridge, Burnside prepared his troops for an assault on Lee’s right flank commanded by Brigadier General David R. Jones. Jones’ Division of 8,000 men stretched along a ridge to Burnside’s west in a line about one mile long.

Ambrose Burnside, Civil War General
General Ambrose Burnside (CSA). Image Source: Library of Congress.

Burnside’s corps started their advance a few minutes after 4 p.m. Their initial thrust pushed the Confederate defenders off of the northern end ridge and into Sharpsburg. Heavy artillery fire on the southern end of the ridge slowed the Union push, but the Confederates grudgingly gave ground. When it seemed that the entire Confederate line might collapse, Major General A. P. Hill‘s Light Division, which had marched fifteen miles, reached the battlefield in time to counter Burnside’s final assault. As Hill’s 3,000 soldiers drove back the inexperienced Federals on the far left of Burnside’s line, darkness descended on the battlefield. By then, the fighting between both exhausted armies subsided.

On September 18, as skirmishing continued on the southern end of the battlefield, the combatants on the northern end of the field helped remove the dead and care for the wounded. Afterward, Lee ordered a retreat and the Army of Northern Virginia began its long trek back to Virginia.

Battle of Antietam Outcome

The Battle of Antietam was the bloodiest single day of combat during the Civil War. Over 3,600 soldiers perished during twelve hours of brutal combat that left neither side with a decisive advantage. Over 3,600 died later from wounds they received on the field. The two armies combined suffered nearly 23,000 casualties, but the losses were proportionally much higher for the Confederacy (29.6%) than for the Union (20.6%). Casualties for the 60,000-man Union Army of the Potomac totaled roughly 12,401 (2,108 killed, 9,540 wounded, and 753 missing). Losses for the 35,000-man Confederate Army of Northern Virginia numbered approximately 10,316 (1,546 killed, 7,752 wounded, and 1,018 missing).

Survivors buried most of the dead in shallow graves on the battlefield. After the war, authorities re-interred the bodies of Union soldiers at Antietam National Cemetery, which was dedicated on September 17, 1867. Later, Southerners exhumed the remains of Confederate soldiers and re-interred them in cemeteries in Frederick and Hagerstown, Maryland, and in Shepherdstown, West Virginia.

Although the battle was tactically a draw, as neither side could claim victory, it was a strategic Union success because McClellan halted Lee’s Maryland Campaign. Although the outcome of the conflict was tactically inconclusive, President Lincoln considered it decisive enough to prompt him to issue his Preliminary Emancipation Proclamation five days later, on September 22, 1862.

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  • Article Title The Battle of Antietam — Bloodiest Day of the Civil War
  • Date September 17, 1862
  • Author
  • Keywords Battle of Antietam, Battle of Sharpsburg
  • Website Name American History Central
  • Access Date June 13, 2024
  • Publisher R.Squared Communications, LLC
  • Original Published Date
  • Date of Last Update March 17, 2024