WIND CAVE NATIONAL PARK

national park in southwestern South Dakota, U.S., established in 1903 to preserve a series of limestone caverns and a tract of unspoiled prairie grassland in the Black Hills. The park's surface area is 28,292 acres (11,449 hectares), and the caves contain 51 miles (82 km) of explored passages. The caverns have two unusual features: a reversible wind that flows alternately in and out of the cave according to outside air pressure, which suggested the name; and beautiful rock formations called boxwork, formed by calcite deposition in unique patterns. The cave's entrance is an artificial one; the only natural entrance is a small hole in the rocks. A game sanctuary like all national reserves, the park has antelope, deer, and even buffalo herds and many species of birds. Vegetation, besides the grassland, includes deciduous and coniferous trees, cactus and other arid-type plants, and wildflowers.