The Black Hills are an outlying subrange of the greater Rocky Mountain system rising from the Great Plains of North America in western South Dakota and eastern Wyoming, United States. Black Elk Peak, which rises to 7,242 feet (2,207 m), is the range's highest summit. The name of the range in Lakota is Pahá Sápa. It encompasses the Black Hills National Forest. It 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. The Black Hills are part of the North American Cordillera, specifically a range within the Rocky Mountain Front of Wyoming, South Dakota, and Montana. The mountains are so called because of their dark appearance from a distance, as they are covered in evergreen trees.