Honoring the men and women who died while serving in the U.S. military, Memorial Day was originally known as Decoration Day when it originated in the years immediately after the Civil War, according to History.com. Waterloo, N.Y., held the first communitywide remembrance on May 5, 1866, decorating soldiers’ graves with flowers and flags. Two years later, Gen. John A. Logan declared a nationwide day of remembrance to be held on May 30. Memorial Day didn’t become a uniform federal holiday until 1971, however, with a floating date to ensure a three-day weekend at the start of summer.