The Battle of Antietam, also known as the Battle of Sharpsburg, was a major Civil War battle that took place on September 17, 1862 near Sharpsburg, Maryland. It was the bloodiest single-day battle in American history and the first major engagement of the Civil War to occur on Northern soil, resulting in around 23,000 casualties for the Union and Confederate forces. The battle pitted Confederate commander Robert E. Lee against Union commander George B. McClellan in the fields and woods around Antietam Creek.