
1885, Charles Rushmore
Eight years after the Manypenny Commission negotiated the treaty which claimed the vast majority of the Sioux Reservation rights, a prominent New York lawyer and businessman took a vacation to the Black Hills to investigate several mining claims and legal titles for properties among his financial interests. While he was hiking he found Mount Rushmore and asked his companion, Bill Challis, what the name of the mountain they were on was.
Bill Challis replied, "It never had a name before, but from now on we'll call it Mount Rushmore." (U.S. National Park Service)
The Native American name for the mountain was "Six Grandfathers".