Black Hills, a somewhat mountainous region located in the southwestern part of South Dakota and extending into Wyoming. The Black Hills are known as one of the best mining regions in the United States. The territory was purchased of the indians in 1876, and mining operations were begun the year following. Gold, silver, copper, lead, iron and a number of valuable building stones are obtained in the region. The annual output of gold is about $4,000,000 and of silver about $3,000,000. See SOUTH DAKOTA.