William MacLeod was born in Alexandria, Virginia, of Scottish immigrant parents. He became interested in painting while studying at the University of Glasgow and upon his return to America traveled widely in the Northeast in search of landscape subjects. In 1854 he returned to Washington and opened an art school where he taught painting and draftsmanship. When forced to close his school at the outbreak of the Civil War, he took a clerical position at the Treasury Department where he remained until 1873 when he became the first curator of collections at the Corcoran Gallery of Art.

Maryland Heights: The Siege of Harpers Ferry is dated 1863 and thus was painted while MacLeod was working at the Treasury Department and during the Civil War. In 1859, before the war began, abolitionist John Brown and several followers attacked the federal arsenal at Harpers Ferry, Virginia (now West Virginia). Brown, who had hoped to incite a slave rebellion, was captured and later hung. The failed attack served as a prelude to the Civil War and Brown became a martyr for the abolitionist cause.

Strategically located at the confluence of the Potomac and Shenandoah Rivers, Harpers Ferry is just sixty miles from Washington. Often described as Washington's "back door," the small town changed hands multiple times during the war. In June 1863, Robert E. Lee launched his second northern campaign leading the Army of Northern Virginia from Richmond into Maryland and later Pennsylvania. In William MacLeod's painting, Union soldiers may be seen camped above the town. Anticipating an attack by Lee's advancing troops, Union forces fortified Maryland Heights, the highest defensive position above Harpers Ferry. The soldier at the center of the painting is pointing in the direction of the advancing Confederate army which, reportedly, could be seen from this location. Lee, however, did not attack, choosing instead to continue his march north without delay. Just a few days later, Confederate and Union forces would meet on the battlefield at Gettysburg.