The Appalachian Mountains ( or ), often called the Appalachians, are a vast system of mountains in eastern North America. 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 Megantic Mountains, Western Newfoundland Mountains, Piedmont, Blue Ridge, Valley and Ridge, Saint Lawrence Valley, Appalachian Plateaus, New England province, and the Adirondack provinces. A common variant definition does not include the Adirondack Mountains, which are often said to have more in common with the Canadian Shield than the Appalachians.

Overview

The range is mostly located in the United States but extends into southeastern Canada, forming a zone from 100 to 300 miles (160 to 480 km) wide, running from the island of Newfoundland 1,500 miles (2,400 km) south-westward to central Alabama in the United States (with foothills in northeastern Mississippi). The system is divided into a series of ranges, with the individual mountains averaging around 3,000 ft (900 m). The highest of the group is Mount Mitchell in North Carolina at , 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. However, 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 Georgia and western South Carolina, as far north as Pennsylvania, and as far west as southern Ohio.

The Ouachita Mountains in Arkansas and Oklahoma were originally part of the Appalachians as well, but were disconnected through geologic history.

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 1. 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 U.S.

After the de Soto expedition in 1540, Spanish cartographers began to apply the name of the tribe to the mountains themselves. The first cartographic appearance of Apalchen is on Diego Gutierrez' map of 1562; the first use for the mountain range is the map of Jacques le Moyne de Morgues in 1565.