premise: Mount Rushmore was built by Gutzon Borglum and his son.
hypothesis: James Lincoln de la Mothe Borglum ( April 9 , 1912 -- January 27 , 1986 ) was an American sculptor , photographer , author and engineer ; he was best known for overseeing the completion of the Mount Rushmore National Memorial after the death in 1941 of the project 's leader , his father , Gutzon Borglum . Mount Rushmore . Sculptor Gutzon Borglum created the sculpture 's design and oversaw the project 's execution from 1927-1941 with the help of his son , Lincoln Borglum . Upon Gutzon Borglum 's death in March 1941 , his son Lincoln Borglum took over as leader of the construction project .