Black Hills, rugged mountains, c.6,000 sq mi (15,540 sq km), enclosed by the Belle Fourche and Cheyenne rivers, SW S.Dak. and NE Wyo., and rising c.2,500 ft (760 m) above the surrounding Great Plains; Harney Peak, 7,242 ft (2,207 m) above sea level, is the highest point in the Black Hills and in South Dakota. The mountains received their name from the heavily forested slopes that appear black from afar. Native Americans, white settlers, and railroad companies depended on wood from the Black Hills for fuel and building material. Gold was discovered in the hills in 1874 by an expedition led by Gen. George Custer, and the resulting gold rush drove out the indigenous population. White settlements grew rapidly after 1876, chiefly in such mining towns in South Dakota as Custer, Deadwood, Lead, Spearfish, and Rapid City, the largest city in the Black Hills. Gold is still mined in the area. Other important minerals found in the hills are uranium, feldspar, mica, and silver. The Black Hills are a major recreational area of the northern plains and a principal tourist spot. Most of the slopes are in two national forests. Wind Cave National Park, Jewel Cave National Monument, and Custer State Park are attractions. The 6,000 ft (1,829 m) Mt. Rushmore, with its gigantic open-air sculpture of Presidents Washington, Jefferson, Lincoln, and T. Roosevelt, is famous throughout the world (see Mount Rushmore National Memorial).