According to History.com Memorial Day, honors men and women who died while serving in the U.S. military. Originally known as Decoration Day, it originated in the years following the Civil War and became an official federal holiday in 1971.
Originally dated May 30 because it was not the anniversary of an particular battle in the Civil War, it is now officially the last Monday of May as a Federal holiday. Many cities and towns hold a parade honoring the military dead. The original Decoration Day in 1868 saw General James Garfield (later to become President of the US and the second president to be assassinated) give a speech and 5000 participants decorated the graves of the 20,000 Union and Confederate soldiers buried in Arlington Cemetery.
Memorial Day was always May 30, until 100 years later the US Congress passed the Uniform Monday Holiday Act, which established Memorial Day as the last Monday in May in order to create a three-day weekend for federal employees; the change went into effect in 1971, according to History.com.
Memorial Day is also considered by many to be the unofficial start of summer. So enjoy your time off, enjoy your picnics, enjoy the retail sales opportunities, but remember the men and women who have sacrificed their lives for the US.