Allegheny, << `al` uh GAY nee, >> Mountains form part of the Appalachian Mountain system of the Eastern United States. They extend southwest from central Pennsylvania through western Maryland, eastern West Virginia, and western Virginia.
The Alleghenies vary in height from about 2,000 feet (610 meters) above sea level in the north to more than 4,800 feet (1,460 meters) in the south. Spruce Knob, the tallest peak in the Alleghenies, rises 4,861 feet (1,482 meters) in West Virginia. The mountains form a divide between streams that flow into the Atlantic Ocean and those that empty into the Gulf of Mexico. The Alleghenies are the eastern edge of the Allegheny Plateau. This plateau is the major source of coal used by iron and steel plants in Pittsburgh and nearby industrial areas. Trees from the mountains, including hickories and maples, are shipped to pulp and paper mills and sawmills in the Allegheny region.
The Alleghenies are one of the most thinly populated regions in the East. Most of the people live in valleys east of the mountains or on the Allegheny Plateau.
The Alleghenies were created about 230 million years ago by disturbances in the earth’s crust. Before that time, the region made up part of a deep ocean trough. About 40,000 feet (12,000 meters) of sediment (loose pieces of minerals and rock) had piled up in this trough. The upper layers of the sediment once formed the floor of dense, swampy forests. The remains of plants from the forests created the thick coal deposits of the Alleghenies and the Allegheny Plateau.
In pioneer times, the Alleghenies were major barriers to transportation. In 1755, the British general Edward Braddock built a road through a mountain pass called Cumberland Narrows, near Cumberland, Maryland. Part of this road, called Braddock’s Road, became part of the National Road, which linked the East Coast and the Ohio River Valley. Today, the pass is the heart of major transportation routes through the Alleghenies. Only a few highways and railroads run through the mountains at other points because of the need to build tunnels to avoid steep grades.
