The first Memorial Day — then called Decoration Day — was celebrated May 30, 1868, three years after the end of the Civil War to honor the Union dead. Compared to a national population of 31.4 million in 1860, the Union dead were estimated at 364,511. Confederate dead totaled at least 159,821, according to "Historical Statistics of the United States (Millennial Edition)."
After World War I, the holiday commemorated all U.S. war dead. In 1971, Memorial Day became an official national holiday. "Historical Statistics" lists war dead by conflicts as follows: the Revolutionary War, 4,435; the War of 1812, 2,260; the Mexican War, 13,283; the Spanish-American War, 2,446; World War I, 116,516; World War II, 405,399; the Korean War, 36,576; the Vietnam War, 58,200; the Persian Gulf War, 382.
In addition, the Pentagon reports 6,809 deaths in the wars in Iraq and Afghanistan and related combat zones as of May 22.