Memorial Day is a United States holiday observed on the last Monday of May. 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 was expanded after World War I to include American casualties of any war. One tradition of Memorial Day is to fly the flag of the United States at half-staff from dawn until noon.

In addition to remembrance, Memorial Day is also used as a time for picnics, barbecues, family gatherings, and sporting events. One of the longest-standing traditions is the running of the Indianapolis 500, which has been held in conjunction with Memorial Day since 1911. Some Americans view Memorial Day as the unofficial beginning of summer and Labor Day as the unofficial end of the season.