<P> The Battle of Antietam / ænˈtiːtəm / , also known as the Battle of Sharpsburg , particularly in the Southern United States , was a battle of the American Civil War , fought on September 17 , 1862 , between Confederate General Robert E. Lee 's Army of Northern Virginia and Union 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 was the bloodiest day in United States history , with a combined tally of 22,717 dead , wounded , or missing . </P>
what was the first major battle of the civil war to be fought on union soil
The Battle of Antietam