Memorial Day is a United States federal holiday observed on the last Monday of May (May 25 in 2009). Formerly known as Decoration Day, it commemorates U.S. men and women who died while in the military service. First enacted to honor Union soldiers of the American Civil War (it is celebrated near the day of reunification after the Civil War), it was expanded after World War I to include American casualties of any war or military action.

Headquarters, Grand Army of the Republic Washington, D.C., May 5, 1868

I. The 30th day of May, 1868, is designated for the purpose of strewing with flowers or otherwise decorating the graves of comrades who died in defense of their country during the late rebellion, and whose bodies now lie in almost every city, village, and hamlet churchyard in the land. In this observance no form or ceremony is prescribed, but posts and comrades will in their own way arrange such fitting services and testimonials of respect as circumstances may permit.