The Battle of Antietam, or Battle of Sharpsburg particularly in the Southern United States, was a battle of the American Civil War fought on September 17, 1862, between Confederate Gen. Robert E. Lee's Army of Northern Virginia and Union Gen. 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 was the bloodiest day in American history, with a combined tally of 22,717 dead, wounded, or missing.
After pursuing Confederate Gen. Robert E. Lee into Maryland, Maj. Gen. George B. McClellan of the Union Army launched attacks against Lee's army who were in defensive positions behind Antietam Creek. At dawn on September 17, Maj. Gen. Joseph Hooker's corps mounted a powerful assault on Lee's left flank. Attacks and counterattacks swept across Miller's Cornfield, and fighting swirled around the Dunker Church. Union assaults against the Sunken Road eventually pierced the Confederate center, but the Federal advantage was not followed up. In the afternoon, Union Maj. Gen.