Originally known to the Lakota Sioux as "The Six Grandfathers" (Tunkasila Sakpe) or "Cougar Mountain" (Igmu Tanka Paha), the mountain was renamed after Charles E. Rushmore, a prominent New York lawyer, during an expedition in 1885. At first, the project of carving Rushmore was undertaken to increase tourism in the Black Hills region of South Dakota. After long negotiations involving a Congressional delegation and President Calvin Coolidge, the project received Congressional approval. The carving started in 1927 and ended in 1941 with no fatalities. As Six Grandfathers, the mountain was part of the route that Lakota leader Black Elk took in a spiritual journey that culminated at Black Elk Peak. Following a series of military campaigns from 1876 to 1878, the United States asserted control over the area, a claim that is 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. Korczak Ziolkowski who sculpted Crazy Horse worked on this project also.