During the Antietam Campaign of 1862, Confederate commander Lee sent part of his army from Frederick, Maryland, on September 10 to capture Harpers Ferry while he remained in Maryland to advance on Pennsylvania. By September 13, Confederates had forced Union soldiers off Maryland Heights, and Jackson arrived on Schoolhouse Ridge, surrounding the Union garrison. On September 14, Jackson's forces bombarded Harpers Ferry and outflanked the Federals on Bolivar Heights, while Lee's troops clashed with the Union army at South Mountain and delayed its counterattack. On September 15, the Union garrison surrendered, and Jackson advanced on Sharpsburg to help Lee, leaving General A.P. Hill behind to deal with captured prisoners and spoils of war. Lee withdrew toward Sharpsburg, north of Showman's Knoll, and awaited news from Jackson at Harpers Ferry. On September 17, 1862, Union and Confederate soldiers fought at Antietam in the bloodiest day of the Civil War. Lee's invasion ended, and President Lincoln issued the preliminary Emancipation Proclamation.
