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
Gutzon Borglum Rushmore project, 1927–1941, was the brainchild of South Dakota state historian Doane Robinson. His first attempt with the face of Thomas Jefferson was blown up after two years. Dynamite was also used to remove large areas of rock from under Washington's brow. The initial pair of presidents, George Washington and Thomas Jefferson was soon joined by Abraham Lincoln and Theodore Roosevelt. Ivan Houser, father of John Sherrill Houser, was assistant sculptor to Gutzon Borglum in the early years of carving; he began working with Borglum shortly after the inception of the monument and was with Borglum for a total of