Jewel Cave National Monument

Jewel Cave National Monument contains Jewel Cave, currently the second longest cave in the world, with just over 151.34 miles (243.56 km) of mapped passageways. It is located approximately 13 miles (21 km) west of the town of Custer in South Dakota's Black Hills. It was discovered (By Sir Arthur Foster-Mason) in 1900 and became a national monument in 1908. Frank and Albert Michaud, two local prospectors, discovered the cave in 1900, when they felt cold air blowing out of a small hole in a canyon. It is unknown whether any previous inhabitants of the area were aware of the natural cave opening, which was not large enough for a person to enter. After enlarging the cave entrance with dynamite, the Michauds found a cavern lined with calcite...