Political map of North America & the Caribbean 17 September 1862 (Battle of Antietam): Having established naval supremacy (Battle of Hampton Roads), Union forces landed on the Virginia peninsula and advanced on Richmond (Peninsula Campaign), only to be smashed by Confederate General Robert E. Lee in the Seven Days Battles. Lee followed up his victory with an invasion of Maryland (Maryland Campaign), but was brought to a halt at the Battle of Antietam/Sharpsburg, the bloodiest single-day battle in American history. Antietam ended the threat to Washington and gave US President Abraham Lincoln confidence to issue the Emancipation Proclamation, officially ending slavery in the Confederacy.