Memorial Day is a national holiday observed in the United States on the last Monday in May. This year, Memorial Day falls on May 27. It is a day when Americans honor the men and women who have died fighting in America’s wars. For most Americans, it also marks the unofficial start of summer. It is a popular weekend for vacationing. Memorial Day traditions include the observance at Arlington National Cemetery. It is the most famous burial place in America. The tradition began on May 30th, 1868, when flowers were placed on the graves of Union and Confederate soldiers in the cemetery. It was called Decoration Day back then.