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 Service took Mount Rushmore under its jurisdiction. Julian Spotts helped with the project by improving its infrastructure. For example, he had the tram upgraded so it could reach the top of Mount Rushmore for the ease of workers. By July 4, 1934, Washington's face had been completed and was dedicated. The face of Thomas Jefferson was dedicated in 1936, and the face of Abraham Lincoln was dedicated on September 17, 1937. In 1937, a bill was introduced in Congress to add the head of civil-rights leader Susan B. Anthony, but a rider was passed on an appropriations bill requiring federal