South Dakota, a north central state of the American Union, surrounded by North Dakota, Minnesota, Iowa, Nebraska, Wyoming, and Montana. The area, 77,650 sq. m., is one and a half times that of England without Wales. Most of the surface is undulating plain, which shows evidence of having in Silurian times been covered by a shallow sea or salt lake. In the W. are the Black Hills, a rugged and mountainous region (3200 sq. m.), whose highest point, Harney Peak, reaches 8200 feet. The 'Bad Lands,' or Mau-vaises Terres, between the north fork of the Platte river in Nebraska and Wyoming, and the south fork of the Cheyenne in this state are covered with rocks of the most fantastic shapes, probably due to the spontaneous firing of large beds of lignite. The Black Hills afford much gold and silver, also tin (the only tin of importance worked in the U.S.), antimony, lead, copper, and other useful minerals, with thermal springs. The winters are cold and dry, with occasional blizzards; in summer the days are hot, the nights usually cool. The rainfall is small, but suffices for the ordinary crops; and pastures are extensive, and oven the Bad Lands are found admirable for cattle-raising. The Missouri, with its tributaries the Cheyenne, White River, and Dakota, is the great river of the country. The population, 98,268 in 1880, was, In 1900, 401,570, including 20,000 Indians on reservations. Sioux Falls is the largest town (10,266). Lead City, Yankton, Aberdeen, and Mitchell have over 5000 inhabitants. Pierre is the capital. South Downs. See Downs.