Definitions vary on the precise boundaries of the Appalachians. The United States Geological Survey (USGS) defines the Appalachian Highlands physiographic division as consisting of thirteen provinces: the Atlantic Coast Uplands, Eastern Newfoundland Atlantic, Maritime Acadian Highlands, Maritime Plain, Notre Dame and Mégantic Mountains, Western Newfoundland Mountains, Piedmont, Blue Ridge, Valley and Ridge, Saint Lawrence Valley, Appalachian Plateaus, New England province, and the Adirondack areas. A common variant definition does not include the Adirondack Mountains, which geologically belong to the Grenville Orogeny and have a different geological history from the rest of the Appalachians.
The range is mostly in the United States (U.S.) but it extends into southeastern Canada, forming a zone from 100 to 300 mi (160 to 480 km) wide, running from the island of Newfoundland 1,500 mi (2,400 km) southwestward to Central Alabama in the United States. The range covers parts of the islands of Saint Pierre and Miquelon, which comprise an overseas territory of France. The system is divided into a series of ranges, with the individual mountains averaging around 3,000 ft (910 m). The highest of the group is Mount Mitchell in North Carolina at 6,684 feet (2,037 m), which is the highest point in the United States east of the Mississippi River.
The term Appalachian refers to several different regions associated with the mountain range. Most broadly, it refers to the entire mountain range with its surrounding hills and the dissected plateau region. The term is often used more restrictively to refer to regions in the central and southern Appalachian Mountains, usually including areas in the states of Kentucky, Tennessee, Virginia, Maryland, West Virginia, and North Carolina, as well as sometimes extending as far south as northern Alabama, Georgia and western South Carolina, and as far north as Pennsylvania, southern Ohio, and parts of southern upstate New York.
While exploring inland along the northern coast of Florida in 1528, the members of the Narváez expedition, including Álvar Núñez Cabeza de Vaca, found a Native American village near present-day Tallahassee, Florida whose name they transcribed as Apalchen or Apalachen . The name was soon altered by the Spanish to Apalachee and used as a name for the tribe and region spreading well inland to the north. Pánfilo de Narváez's expedition first entered Apalachee territory on June 15, 1528, and applied the name. Now spelled "Appalachian," it is the fourth-oldest surviving European place-name in the US.