Wind Cave National Park

Location: South Dakota

Year Established: 1903

Area: 28,295.03 acres (114.5 km2)

Annual Visitors: 542,022

Wind Cave is distinctive for its calcite fin formations called boxwork and needle-like growths called frostwork. The cave, which was discovered by a sound like that of wind coming from a hole in the ground, is the world's densest cave system. Above ground is a mixed-grass prairie with animals such as bison, black-footed ferrets, and prairie dogs and ponderosa pine forests home to cougars and elk.