In short
On September 17, 1862, Union and Confederate forces clashed near Sharpsburg, Maryland, in the deadliest single day in American military history. Robert E. Lee's invasion of the North was halted, giving Abraham Lincoln the strategic opening he needed to issue the Emancipation Proclamation.
How it unfolded.
The five-minute version
What actually happened.
The Battle of Antietam, also called the Battle of Sharpsburg, particularly in the Southern United States, took place during the American Civil War on September 17, 1862, between Confederate General Robert E. Lee's Army of Northern Virginia and Union Major General George B. McClellan's Army of the Potomac near Sharpsburg, Maryland, and Antietam Creek. Part of the Maryland Campaign, it was the first field army–level engagement in the Eastern Theater of the American Civil War to take place on Union soil. It remains the bloodiest day in American history, with a tally of 22,726 dead, wounded, or missing on both sides. Although the Union Army suffered heavier casualties than the Confederates, the battle was a major turning point in the Union's favor.
As it was happening
11 voices, 30 days.
One beat at a time. Click any dot on the timeline to jump, press play for autoplay, or use the arrow keys to step.
Lee begins invasion of Maryland
Confederate General Robert E. Lee crosses the Potomac River with the Army of Northern Virginia, seeking to carry the war into Union territory and potentially secure foreign recognition for the Confederacy.
Voices from this moment (1)
Lee begins invasion of Maryland
Sep 4
“Confederate General Robert E.”
As it was happening
11 voices, 30 days.
Day 0 · September 4, 1862
Lee begins invasion of Maryland
Confederate General Robert E. Lee crosses the Potomac River with the Army of Northern Virginia, seeking to carry the war into Union territory and potentially secure foreign recognition for the Confederacy.
“Confederate General Robert E.”
- Lee begins invasion of Maryland, Sep 4
Day 9 · September 13, 1862
Special Order 191 discovered
Union soldiers find a copy of Lee's battle plans wrapped around cigars abandoned by Confederate troops. The document reveals Lee's troop dispositions and allows McClellan to anticipate Confederate movements.
“Union soldiers find a copy of Lee's battle plans wrapped…”
- Special Order 191 discovered, Sep 13
Day 13 · September 17, 1862
Battle of Antietam begins
At dawn, Union forces under McClellan attack Lee's position along the Antietam Creek. The battle unfolds in three major phases: an assault on the Confederate left, fighting at the Sunken Road in the center, and a assault on the right flank.
Day 13 · September 17, 1862
Bloody Lane engagement
Fierce fighting erupts at a sunken road (later called Bloody Lane) where Confederate troops hold their ground. Union assaults suffer heavy casualties but eventually dislodge the defenders, though momentum stalls.
Day 13 · September 17, 1862
A.P. Hill arrives; battle concludes
Confederate General Ambrose Powell Hill's division arrives from Harpers Ferry in time to check a Union breakthrough on the right. Fighting ends as darkness falls; McClellan does not commit his reserves to pursue victory.
“At dawn, Union forces under McClellan attack Lee's position…”
- Battle of Antietam begins, Sep 17
“Fierce fighting erupts at a sunken road (later called…”
- Bloody Lane engagement, Sep 17
“Confederate General Ambrose Powell Hill's division arrives…”
- A.P. Hill arrives; battle concludes, Sep 17
Day 14 · September 18, 1862
Lee withdraws to Virginia
After a night of tense standoff, Lee withdraws the Army of Northern Virginia across the Potomac River back into Virginia. McClellan does not pursue aggressively.
“Great Battle Near Sharpsburg - Union and Confederate Forces…”
- The New York Times, Sep 18
“The Battle of Sharpsburg - Lee's Army Repels the Yankee…”
- The Richmond Enquirer, Sep 20
“After a night of tense standoff, Lee withdraws the Army of…”
- Lee withdraws to Virginia, Sep 18
Day 18 · September 22, 1862
Lincoln issues preliminary Emancipation Proclamation
Taking advantage of the battle outcome, Abraham Lincoln announces the preliminary Emancipation Proclamation, declaring slaves in rebellious states would be freed effective January 1, 1863. This reframes the war's purpose.
“The American Struggle - A Furious Engagement at Maryland”
- The Times of London, Oct 2
“The Battle of Antietam - Pictorial Summary of the Bloodiest…”
- Harper's Weekly, Oct 4
“Taking advantage of the battle outcome, Abraham Lincoln…”
- Lincoln issues preliminary Emancipation Proclamation, Sep 22
The numbers.
5 numbers that anchor the scale.
By the numbers
The countable parts.
Estimated casualties
0 killed, wounded, and missing combined
Union casualties
0
Confederate casualties
0
Troop strength (Union)
0
Troop strength (Confederate)
0
Front pages.
3 outlets carried the story: The New York Times, The Richmond Enquirer, The Times of London.
Media coverage
What the world was reading.
4 pieces, ranked by how much they shaped the discourse.
The New York Times
Newspaper · United States - North · Sep 18, 1862
"Great Battle Near Sharpsburg - Union and Confederate Forces Engage in Bloodiest Day of the War"
The armies of General McClellan and General Lee met in furious combat on the banks of the Potomac near Sharpsburg, Maryland, on Wednesday last, in what observers reckon the most terrible single day of carnage yet witnessed on an American battlefield.
- Sep 20, 1862
The Richmond Enquirer
Newspaper · United States - South
"The Battle of Sharpsburg - Lee's Army Repels the Yankee Onslaught"
Synthesized from period reporting - Our valiant General Lee, commanding the Army of Northern Virginia, has met the Federal host under McClellan and turned back their invasion of the South, though at terrible cost to our brave soldiers.
- Oct 4, 1862
Harper's Weekly
Magazine · United States - North
"The Battle of Antietam - Pictorial Summary of the Bloodiest Day"
Synthesized from period reporting - Our artists and correspondents provide detailed accounts and illustrations of the fierce engagement along the creek near Sharpsburg, where upwards of twenty thousand casualties fell in a single day of battle.
- Oct 2, 1862
The Times of London
Newspaper · United Kingdom
"The American Struggle - A Furious Engagement at Maryland"
Dispatches from our correspondent in Washington indicate that the recent battle near Sharpsburg has proven inconclusive, with both Union and Confederate forces claiming advantage, though the scale of loss on both sides gives pause to any notion of swift resolution to this fratricidal contest.
Captured in time.
Captured before it changed
The web as it looked, the day it happened.
Wayback Machine snapshots of the pages people actually loaded that day. Click any card to open the archive at full size.
Sources & citations.
Sources
Where this came from.
Every claim on this page traces to a public, license-clean source. We don't asterisk well.
Wikipedia
1 source- 1.Battle of Antietam
en.wikipedia.org