1864: A Confederate prisoner of war was buried on the grounds of Arlington House, now Arlington National Cemetery. The prisoner, who had died at a local hospital, was the first soldier buried at the cemetery, located on the Potomac River opposite Washington, D.C. It now contains the graves of soldiers from every war in which the United States has participated, including the American Revolution. Arlington House was built in 1802 by George Washington Parke Custis, adopted son of George Washington. In 1831, Custis' daughter, Mary Anna, married Lieutenant Robert E. Lee in the main hall of the mansion. The couple resided there until 1861, when Lee took command of Confederate troops in the Civil War. (Source: Library of Congress)