EVERY DAY – UNTIL 5/27/2019 (USA Holiday) Honors all Americans who have died in all wars. || Memorial Day is a federal holiday observed annually in the United States on the last Monday of May. Formerly known as Decoration Day, it originated after the American Civil War to commemorate the fallen Union soldiers of the Civil War. (Southern ladies organizations and southern schoolchildren had decorated Confederate graves in Richmond and other cities during the Civil War, but each region had its own date. Most dates were in May.) By the 20th century Memorial Day had been extended to honor all Americans who have died in all wars.