Encroaching miners and settlers triggered a number of Indian wars, ending with the Wounded Knee Massacre in 1890.
Key events in the 20th century included the Dust Bowl and Great Depression, increased federal spending during the 1940s and 1950s for agriculture and defense, and an industrialization of agriculture that has reduced family farming.
At times the Black Hills are combined with the rest of western South Dakota, and people often refer to the resulting two regions divided by the Missouri River as West River and East River.
Erosion from the Black Hills, marine skeletons which fell to the bottom of a large shallow sea that once covered the area, and volcanic material all contribute to the geology of this area.), with peaks that rise from 2,000 to 4,000 feet (600 to 1,200 m) above their bases.
The Black Hills are the location of Black Elk Peak (7,242 ft or 2,207 m above sea level), the highest point in South Dakota and also the highest point in the United States east of the Rocky Mountains.
The Coteau des Prairies is a plateau bordered on the east by the Minnesota River Valley and on the west by the James River Basin.
The Dissected Till Plains, an area of rolling hills and fertile soil that covers much of Iowa and Nebraska, extends into the southeastern corner of South Dakota.