The Battle of Antietam, also known as the Battle of Sharpsburg, took place on September 17, 1862 near Sharpsburg, Maryland. It pitted the Union Army led by General George B. McClellan against the Confederate Army led by General Robert E. Lee in the bloodiest single day battle of the American Civil War. Over 23,000 soldiers were killed, wounded, or captured in the 12-hour battle, which ended inconclusively with heavy casualties on both sides. Despite failing to defeat Lee's army, the Union victory halted Lee's invasion of the North and allowed President Lincoln to issue the Emancipation Proclamation, declaring all slaves in Confederate states free.