The Appalachian Mountains, often called the Appalachians, are a system of mountains in eastern to northeastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They once reached elevations similar to those of the Alps and the Rocky Mountains before experiencing natural erosion. The Appalachian chain is a barrier to east–west travel, as it forms a series of alternating ridgelines and valleys oriented in opposition to most highways and railroads running east–west.
|Elevation||6,684 ft (2,037 m)|
|Length||1,500 mi (2,400 km)|
|Countries||United States and Canada|
|Provinces/States||Newfoundland and Labrador, Saint Pierre and Miquelon, Québec, Nova Scotia, New Brunswick, Maine, New Hampshire, Vermont, Massachusetts, Connecticut, New York, New Jersey, Pennsylvania, Maryland, Washington, D.C., Delaware, Virginia, West Virginia, Ohio, Kentucky, Tennessee, North Carolina, South Carolina, Georgia and Alabama|
|Orogeny||Taconic, Acadian, Alleghanian|
|Age of rock||Ordovician–Permian|
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, and New England province. The Appalachians do not include the Adirondack Mountains. The Adirondacks are a part of the Canadian Shield and belong to the Grenville Orogeny; they are a distinct and growing range separate from the Appalachians.