Memorial Day is tomorrow. The national holiday was declared by Congress in 1971 and set the date as the last Monday in May each year. The holiday originated shortly after the Civil War, according to the U.S. Department of Veteran’s Affairs. The day was initially called Decoration Day, a day when the nation decorated the graves of the war dead with flowers. In 1871, the first large observance of Decoration Day was held at Arlington National Cemetery. This weekend in Washington the Avenue of Flags is on dispaly at Elm Grove Cemetery, with more than 400 flags flying.