The Battle of Antietam

What happened

Near Sharpsburg, Maryland, Lee's first invasion of the North met McClellan's Army of the Potomac. In the single bloodiest day in American history, more than 23,000 men were killed, wounded, or missing. Lee was forced to withdraw to Virginia.

Why it matters

The strategic Union victory halted Lee's invasion and gave Lincoln the moment he needed to issue the preliminary Emancipation Proclamation.

Sources

• National Park Service. A Short Overview of the Battle of Antietam · Reputable source