Mount Rushmore community. Recent pine beetle infestations have threatened the forest. Mount Rushmore is largely composed of granite. The memorial is carved on the northwest margin of the Black Elk Peak granite batholith in the Black Hills of South Dakota, so the geologic formations of the heart of the Black Hills region are also evident at Mount Rushmore. The batholith magma intruded into the pre-existing mica schist rocks during the Proterozoic, 1.6 billion years ago. Coarse grained pegmatite dikes are associated with the granite intrusion of Black Elk Peak and are visibly lighter in color, thus explaining the light-colored streaks on the
Mount Rushmore and secured federal funding; construction began in 1927, and the presidents' faces were completed between 1934 and 1939. Gutzon Borglum died in March 1941, and his son Lincoln took over as leader of the construction project. Each president was originally to be depicted from head to waist, but lack of funding forced construction to end on October 31, 1941. Mount Rushmore attracts more than two million visitors annually. 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