West Virginia lies within two divisions of the Appalachian Highlands. Most of the eastern panhandle, which is crossed by the Allegheny Mountains, is in the Ridge and Valley region. The remainder, or more than two-thirds of the state, is part of the Allegheny Plateau, to the west of a bold escarpment known as the Allegheny Front, and tilts toward the Ohio River.
The mean elevation of West Virginia is 1,500 ft (458 m), higher than any other state east of the Mississippi River. Its highest point, Spruce Knob, towers 4,861 ft (1,483 m) above sea level. Major lowlands lie along the rivers, especially the Potomac, Ohio, and Kanawha. A point on the Potomac River near Harpers Ferry has the lowest elevation, only 240 ft (73 m) above sea level. West Virginia has no natural lakes.
Most of the eastern panhandle drains into the Potomac River. The Ohio and its tributaries—the Monongahela, Little Kanawha, Kanawha, Guyandotte, and Big Sandy—drain most of the Allegheny Plateau section. Subterranean streams have carved out numerous caverns—including Seneca Caverns, Smoke Hole Caverns, and Organ Cave—from limestone beds.
During the Paleozoic era, when West Virginia was under water, a 30,000-ft (9,000-m) layer of rock streaked with rich coal deposits was laid down over much of the state. Alternately worn down and uplifted during succeeding eras, most of West Virginia is thus a plateau where rivers have carved deep valleys and gorges and given the land a rugged character.