Antietam: The Bloodiest Day in American History
Lee's first invasion of the North ends at Sharpsburg after 23,000 men fall in a single day
Quick facts
- Location
- Sharpsburg, Maryland
- Union commander
- George B. McClellan
- Confederate commander
- Robert E. Lee
- Casualties
- About 23,000 in one day
What happened
After his victory in the Seven Days and a second win at Second Bull Run in August, Robert E. Lee crossed the Potomac into Maryland, hoping a Confederate victory on Northern soil might win European recognition for the Confederacy. A Union soldier found a copy of Lee's marching orders wrapped around cigars, giving McClellan advance knowledge of Lee's divided forces, but McClellan moved too cautiously to fully exploit the advantage. The armies collided at Antietam Creek near Sharpsburg, Maryland on September 17, 1862, in twelve hours of fighting across the Cornfield, the Sunken Road, and Burnside's Bridge. By nightfall roughly 23,000 men were killed, wounded, or missing, the bloodiest single day in American history. Lee's battered army withdrew back across the Potomac into Virginia that night.
Why it matters
Although tactically closer to a draw than a clear Union victory, Lee's retreat gave Lincoln the battlefield success he had been waiting for to issue the preliminary Emancipation Proclamation five days later, and it ended the Confederacy's best chance of winning British or French recognition.
How we know
The National Park Service's Antietam National Battlefield history and its dedicated casualties page compile the toll from official Union and Confederate medical and unit reports.
Sources
- National Park Service. A Short Overview of the Battle of Antietam · Reputable sourcenps.gov · The domain "nps.gov" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
- Antietam National Battlefield, National Park Service. Casualties · Reputable sourcenps.gov · The domain "nps.gov" is on our Reputable source registry.
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