Explore images of the battlefield of Antietam. On September 17, 1862, Confederate General Robert E. Lee and Maj. General George McClellan faced off in a battlefield near Sharpsburg, Maryland. The battle of Antietam was the single bloodiest day of the Civil War, with 22,720 men killed, wounded, or missing after 12 hours of fighting. The battle was considered a draw from a military perspective, but the Union declared victory. On January 1, 1863, President Abraham Lincoln issued the Emancipation Proclamation, declaring that all slaves in the south were free.