Mount Rushmore still disputed on the basis of the 1868 Treaty of Fort Laramie (see section "Controversy" below). Among 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 Charles Rushmore, David Swanzey (husband of Carrie Ingalls), and Bill Challis. Historian Doane Robinson conceived the idea for Mount Rushmore in 1923 to promote tourism in South Dakota. In 1924, Robinson persuaded sculptor Gutzon Borglum to travel to the Black Hills region to ensure the carving could be accomplished. Borglum had been involved in sculpting the
Mount Rushmore selected Mount Rushmore as the site for several reasons. The rock of the mountain is composed of smooth, fine-grained granite. The durable granite erodes only every 10,000 years, thus was more than sturdy enough to support the sculpture and its long-term exposure. The mountain's height of above sea level made it suitable, and because it faces the southeast, the workers also had the advantage of sunlight for most of the day. The Mount Rushmore area is underlain by well drained alfisol soils of very gravelly loam (Mocmount) to silt loam (Buska) texture, brown to dark grayish brown. Mount Rushmore has