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
Washington State Route 206 Washington State Route 206 State Route 206 (SR 206, named the Mount Spokane Park Drive) is a state highway serving Mount Spokane State Park in the U.S. state of Washington. Beginning at U.S. Route 2 (US 2) north of Mead, the highway travels east through unincorporated Spokane County and northeast into the Selkirk Mountains, ending at the entrance to Mount Spokane State Park. The roadway, first constructed in the 1890s and reconstructed several times, was designated as SR 206 during the 1964 highway renumbering. SR 206 begins as Mount Spokane Park Drive at an intersection with US 2 north of