U.S. Navy Rear Adm. Daniel Fillion, U.S. Strategic Command director of global operations, greets veterans from American Legion Post 56 during a Memorial Day ceremony at Oak Hill Cemetery, May 28, 2018, in Plattsmouth, Neb. The tradition of honoring fallen war veterans dates back to May 5, 1868, when the head of the Grand Army of the Republic, an organization of Union veterans, established Decoration Day as a time for the nation to decorate the graves of the fallen military with flowers. In 1971, Memorial Day was declared a national holiday by Congress to be observed on the last Monday of May.