A park ranger talked about the Maryland Monument on the Antietam National Battlefield. The monument depicts scenes of the battle in which troops from the state were engaged on both sides of the conflict. The National Park Service was commemorating the 150th anniversary of the Battle of Antietam. The battle on September 17, 1862, was the bloodiest day of fighting in American history. President Lincoln took advantage of the Union strategic victory to issue the preliminary Emancipation Proclamation a few days later.