Appalachian Mountains, mountain system of Northeastern America, about 1,800 mi (2,897 km) long and 120–375 mi (193–603 km) wide, stretching south from Newfoundland to central Alabama. Major ranges of the north include the Notre Dame, Green, and White mountains. The central area has the Allegheny Mountains and part of the Blue Ridge Mountains. The south contains the south Blue Ridge, Cumberland, Black, and Great Smoky mountains. The highest peak is Mt. Mitchell (6,684 ft/2,037 m) in North Carolina. Appalachian forests yield much timber, and rich deposits of coal and iron have stimulated growth of industrial areas like Birmingham, Ala., and Pittsburgh, Pa. In the early years of the United States, the Appalachians were a barrier to westward expansion, but the Connecticut, Hudson, Delaware, and other rivers have cut deep gaps in the ranges.