Rapid City, city (1990 pop. 54,523), seat of Pennington co., SW S.Dak., on Rapid Creek, in an irrigated farm region served by the Bureau of Reclamation's Rapid Valley project; founded 1876 after the discovery of gold nearby, inc. 1882. It is the trade and transportation center of an extensive lumbering, ranching, and mining (gold, silver, feldspar, bentonite, mica, and uranium) area. Wood products, sand and gravel, small arms ammunition and gun stocks, gold and silver jewelrey, food products, construction materials, and limestone are produced. Nearby Ellsworth Air Force Base is a major source of employment. The city is also the tourist center of the Black Hills and the gateway to many attractions, including Mount Rushmore National Memorial, Badlands National Park, and Wind Cave National Park. The South Dakota School of Mines and Technology, National American Univ., a Sioux museum, and a pioneer museum are in Rapid City. In 1972 the city was struck by a severe flash flood in which more than 200 lives were lost.