Jewel Cave National Monument

In 1900 Frank and Albert Michaud, prospectors working Hell Canyon west of Custer, felt cold air blowing from a small hole in the rock. They blasted it open and found a chamber lined with calcite crystals that glittered in their lamps, and named it Jewel Cave. They filed a mining claim, built a lodge and a trail and tried to sell tours, but visitors were few, and after Theodore Roosevelt proclaimed the cave a national monument on February 7, 1908, the first ever made to protect a cave, they sold their claim to the government for $750.

For half a century the monument was thought to be a small cave, about two miles long. In 1959 Herb and Jan Conn, rock climbers from Custer, began exploring with the geologist Dwight Deal, and within two years they had mapped fifteen miles. They kept going for two decades, crawling, chimneying and squeezing, and had found, named and surveyed more than sixty-four miles by 1979. Their routes became the tours.

Volunteer survey teams carry the work on, adding a few miles most years, and the mapped cave now runs to more than 220 miles, among the five longest known on Earth. All of it lies beneath about four square miles of hillside, and studies of the air moving through the entrance suggest that what has been found is only a few percent of the whole.