The Battle of ANTIETAM, which took place on September 17, 1862, was a major Civil War battle site. It was the first battle to take place on Union soil and resulted in the bloodiest single-day battle in American history. The Union forces were led by General George McClellan and the Confederate forces were led by General Robert E. Lee. The battle ended in a draw, but it was a strategic victory for the Union as it prevented Lee from invading Maryland.