Memorial Day is a federal holiday in the United States for remembering the men and women who died while serving in the country's armed forces. The holiday, which is celebrated every year on the last Monday of May, was formerly known as Decoration Day and originated after the American Civil War to commemorate the Union and Confederate soldiers who died in the war. By the 20th century, Memorial Day had been extended to honor all Americans who died while in the military service. It typically marks the start of the summer vacation season, while Labor Day marks its end. Many people visit cemeteries and memorials, particularly to honor those who have died in military service. Many volunteers place an American flag on each grave in national cemeteries. Annual Decoration Days for particular cemeteries are held on a Sunday in late spring or early summer in some rural areas of the American South, notably in the mountain areas. In cases involving a family graveyard where remote ancestors as well as those who were deceased more recently are buried, this may take on the character of an extended family reunion to which some people travel hundreds of miles.