The Black Hills are isolated eroded mountain region in western South Dakota and northeastern Wyoming, U.S., lying largely within Black Hills National Forest. The hills lie between the Cheyenne and Belle Fourche rivers and rise about 3,000 feet (900 metres) above the surrounding plains. They culminate in Black Elk Peak (7,242 feet [2,207 metres]), the highest point in South Dakota. The Black Hills formed as a result of an upwarping of ancient rock, after which the removal of the higher portions of the mountain mass by stream erosion produced the present-day topography.

Source: Britannica