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 would be the single bloodiest day of the Civil War, with 23,000 men killed, wounded, or missing after 12 hours of fighting. The battle would end in a draw. Five days later, President Abraham Lincoln would issue his Emancipation Proclamation, declaring that all slaves in the south were free.