By editor
Jefferson County
Three hundred and fifty million years ago, a shallow, warm sea covered what is now Montana. The calcium-rich shells of marine organisms accumulated on the seafloor, compressing over eons into the Mission Canyon Limestone. Much later, slightly acidic groundwater seeped into fractures, dissolving the rock and hollowing out massive chambers. Mineral-rich water continued to drip from the ceiling, leaving behind microscopic deposits of calcite that grew into stalactites and stalagmites.
Visitor Access
This is a highly regulated State Park. Collecting is strictly forbidden; there is a ten-thousand-dollar fine for simply touching the delicate cave formations. Access to the caverns is by guided tour only, available from May through September for a ten-dollar fee, plus the eight-dollar park entry. The park also offers excellent above-ground hiking and camping.