The Western Hill Section includes the Allegheny Plateau from the Ohio River to the mountains. The southern portion is more rugged than the northern, a result of strata resistent to erosion.
Streams are dendritic and hills and tributaries are laid out randomly, as any hiker can attest.
The Allegheny Mountain and Upland Section encompasses the mountain ranges oriented northeast-southwest and the deep valleys. These are the highest mountains in the state and typically are covered with Northern Hardwoods and Northern Evergreens . Hardwoods exist from the lower levels of evergreens to around 2,500 feet. The principal hardwoods are sugar maple, yellow birch, and beech, and many other species thrive in smaller numbers. The highest areas are characterized by subalpine tablelands such as are on Allegheny Front Mountain, which includes Dolly Sods.