Side View of Mt. Rushmore

Though the area receives about 18 inches (460 mm) of precipitation on average per year, alone it is not enough to support the abundant animal and plant life. Trees and other plants help to control surface runoff. Dikes, seeps, and springs help to dam up water that is flowing downhill, providing watering spots for animals. In addition, stones like sandstone and limestone help to hold groundwater, creating aquifers.

As Six Grandfathers, the mountain was part of the route that Lakota leader Black Elk took in a spiritual journey that culminated at Harney Peak. Following a series of military campaigns from 1876 to 1877, the United States asserted control over the area, a claim that is still disputed based on the 1868 Treaty of Fort Laramie (see Controversy below). Among white American settlers, the peak was known variously as Cougar Mountain, Sugarloaf Mountain, Slaughterhouse Mountain, and Keystone Cliffs. It was named Mount Rushmore during a prospecting expedition by Rushmore, David Swanzey (whose wife Carrie was the sister of author Laura Ingalls Wilder), and Bill Challis.

 
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