South Carolina is divided into two major regions by the fall line that runs through the center of the state from Augusta, Georgia, to Columbia and thence to Cheraw, near the North Carolina border. The area northwest of the line, known as the upcountry, lies within the Piedmont Plateau; the region to the southeast, called the low country, forms part of the Atlantic Coastal Plain. The rise of the land from ocean to the fall line is very gradual: Columbia, 120 mi (193 km) inland, is only 135 ft (41 m) above sea level. In the extreme northwest, the Blue Ridge Mountains cover about 500 sq mi (1,300 sq km); the highest elevation, at 3,560 ft (1,086 m), is Sassafras Mountain.
Among the many artificial lakes, mostly associated with electric power plants, is Lake Marion, the state's largest, covering 173 sq mi (48 sq km). Three river systems—the Pee Dee, Santee, and Savannah—drain most of the state. No rivers are navigable above the fall line.