Jewel Cave National Monument, the Underground Treasure

Drive the pine hills west of Custer and nothing on the surface gives it away. A modest visitor center, two hiking trails, a canyon or two. Then an elevator door opens 200-some feet down, and you are standing inside the fifth longest cave in the world: more than 220 miles of mapped passages stacked in a three-dimensional maze, walls lined with calcite crystal that glints wherever light lands.

The name is honest. When two prospectors squeezed through a whistling opening in Hell Canyon in 1900, their candlelight caught walls that glittered like gems, and they staked a mining claim on the “jewels.” The crystals turned out to be worth far more left in place. Within a decade the cave was a national monument, and more than a century later its explorers are still nowhere near the end of it.

Every trip underground here is a ranger-guided tour, from a 20-minute chamber visit by elevator to a crawl that takes most of an afternoon, so a good visit starts with picking the right tour and booking it early. This page is your way into the whole story: how the cave formed, who found it, why the map keeps growing, and how to plan a day here. The three short guides below handle the tour logistics.

Who discovered Jewel Cave?

In the summer of 1900, two local prospectors, brothers Frank and Albert Michaud, noticed something strange while looking for mining prospects in Hell Canyon: wind whistling out of a small natural opening in the rock. They enlarged the hole, climbed in, and found walls glittering with calcite crystals that looked like jewels by candlelight. They did what prospectors do and filed a mining claim.

The crystals proved unprofitable to mine, so the brothers pivoted to something new for the Black Hills: guided cave tours, among the first in the region. The cave’s beauty and scientific value drew national attention, and in 1908 President Theodore Roosevelt proclaimed Jewel Cave a national monument under the Antiquities Act, the first cave in the United States protected that way.

The U.S. Forest Service managed the monument at first, handing it to the National Park Service in 1933. During the Great Depression, Civilian Conservation Corps crews built a ranger cabin, improved the trails, and set a stone stairway into the cave, groundwork that still shapes how visitors experience the historic entrance today.

How big is Jewel Cave, really?

Bigger than anyone can say. The mapped figure stood at 220.33 miles as of September 7, 2024, which ranks Jewel Cave fifth longest in the world. But the cave breathes: air rushes in and out of its entrances as surface pressure changes, and studies of that airflow suggest explorers have found only about 3 to 5 percent of what is down there.

That means the map is not a finished document. It is a frontier that volunteer cavers push outward on multi-day expeditions, one surveyed foot at a time, and it has been growing for more than a century. The story of how the survey crossed its 200th mile, and what it takes to camp underground to keep exploring, gets its own page: the Jewel Cave 200-mile milestone.

What is there to do above ground?

Start at the visitor center, the gateway to the cave and fully accessible: interpretive exhibits, an information desk staffed by rangers and volunteers, the NPS Passport stamp, and the park store BHPFA runs for the monument. It is open year-round. Here is the full schedule.

Visitor center hours

• Summer, May 25 through September 7, 2026: open daily, 8:00 am to 5:30 pm Mountain Time.
• September 8, 2026 through spring: Tuesday through Saturday, 8:30 am to 4:30 pm. Closed Sundays and Mondays.
• Holiday closures: Thanksgiving (November 26, 2026), Christmas Day (December 25, 2026), and New Year’s Day (January 1, 2027).

The main entrance gate closes promptly at 5:30 pm, so plan your hike or your time on the surface trails to be back out before then. Cave tour times run on their own seasonal schedule and are listed above.

Hours confirmed against the National Park Service on September 8, 2026. We run the park store inside this visitor center, so if you ever find this out of date, tell us at [email protected] and we will fix it.

Two self-guided trails begin near the visitor center. The Roof Trail is an easy quarter-mile paved loop through the ponderosa pines, with benches and a small hill’s worth of views; a few moderate grades keep it from being classed as wheelchair accessible. The Canyons Trail is the real hike: a 3.5-mile loop through Lithograph Canyon and Hell Canyon, rated easy to moderate, with some steep segments and stairs. It passes the cave’s historic natural entrance and an old ranger cabin, and rewards you with wildflower meadows in summer. Watch for mule deer, wild turkeys, and the bighorn sheep that have been reintroduced to the area. In winter, the park loans snowshoes for the same trails under snow.

Who takes care of Jewel Cave?

The National Park Service manages the monument, and much of its work happens out of sight: monitoring the nine bat species that use the cave and guarding against white-nose syndrome, studying the cave’s climate and water to understand how the surface affects the underground, switching to LED lighting that discourages algae from growing on formations, and keeping tour groups small and on designated paths. You help simply by following ranger instructions and never touching the formations; the oils on human skin damage them.

Black Hills Parks & Forests Association is the monument’s nonprofit cooperating association. BHPFA runs the park store at the visitor center and the Jewel Cave collection online, and puts the money back into the place, funding research, interpretation, and education programs at the monument. Buying a book after your tour or becoming a member is a small act with a direct, local return.