Alleghany, or Appalachian Mountains, a mountain system that stretches from Cape Gaspe, on the Gulf of St. Lawrence, to Alabama, in the Gulf of Mexico, a distance of 1,300 miles. It may be divided into three sections; the Northern, from Cape Gaspe to New York, includes the Adirondacks, the Green and the White Mountains; the Central, from New York to the valley of the New River, contains part of the Blue Ridge, the Alleghanies proper, and many smaller parallel ranges; the Southern, from the New River to the Gulf of Mexico, embraces the smaller half of the Blue Ridge, the Black, the Smoky, and the Unaka Mountains. The system then traverses many states, and forms the watershed between the basin of the Mississippi and the rivers flowing into the Atlantic. The average height of the component ranges is under 3,000 feet, but Mount Washington, in New Hampshire, rises to 6,620 feet. Geologically the Alleghanies are made up of granite, gneiss, mica, clay, slate, and primary limestones. They contain valuable mines of coal and iron, and are usually wooded to their summits, and intersected by rich valleys. The name Alleghany was adopted by the English in the North from the Indians, and means "endless."