Appalachian Mountains

The Appalachian Mountains,[lower-alpha 1] 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.[4][5] 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.

Appalachian Mountains
August 2007 view from the slopes of Back Allegheny Mountain, looking east; visible are Allegheny Mountain (in the Monongahela National Forest of West Virginia, middle distance), and Shenandoah Mountain (in the George Washington National Forest of Virginia, far distance)
Highest point
PeakMount Mitchell
Elevation6,684 ft (2,037 m)
Length1,500 mi (2,400 km)
CountriesUnited States and Canada
Provinces/StatesNewfoundland and Labrador[1][2], 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
Range coordinates40°N 78°W
OrogenyTaconic, Acadian, Alleghanian
Age of rockOrdovicianPermian

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.[6][7] 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.[8][9][10]