Mount Rushmore a humid continental climate ("Dwb" in the Köppen climate classification). It is inside a USDA Plant Hardiness Zone of 5a, meaning certain plant life in the area can withstand a low temperature of no less than . The two wettest months of the year are May and June. Orographic lift causes brief but strong afternoon thunderstorms during the summer. Tourism is South Dakota's second-largest industry, and Mount Rushmore is the state's top tourist attraction. In 2012, 2,185,447 people visited the park. In the 1950s and 1960s, Sioux Benjamin Black Elk (son of medicine man Black Elk) was the "Fifth Face
Mount Rushmore of Mount Rushmore", posing for photographs with thousands of tourists. He became one of the most photographed people in the world. The ongoing conservation of the site is overseen by the National Park Service. Physical efforts to conserve the monument have included replacement of the sealant applied originally by Gutzon Borglum, which had proved ineffective at providing water resistance. The components of Borglum's sealant included linseed oil, granite dust, and white lead, but a modern silicone replacement is now used, disguised with granite dust. In 1998, electronic monitoring devices were installed to track movement in the topology of the sculpture