Hot springs in Wyoming

Wyoming holds the largest concentration of hydrothermal features in the country. Yellowstone National Park, in the northwest corner of the state, contains more than 10,000 hydrothermal features, including geysers, hot springs, mudpots and fumaroles, according to the National Park Service. They are heated by the Yellowstone hotspot, a body of partly molten rock beneath the Yellowstone Caldera, which formed in an eruption about 640,000 years ago, according to the U.S. Geological Survey's Yellowstone Volcano Observatory. Outside the park, thermal springs rise along faults and folds in the basins, most notably at Thermopolis in the Bighorn Basin.

Most of the state's thermal water is on public land. Yellowstone and Grand Teton national parks are managed by the National Park Service, and inside Yellowstone visitors must stay on boardwalks and designated trails in thermal areas. The Bridger-Teton and Shoshone national forests surround the parks. At Thermopolis, Hot Springs State Park, run by Wyoming State Parks, holds the Big Spring; the Shoshone and Arapaho ceded the springs to the federal government in an 1896 agreement that kept access to the mineral water free to the public. Springs on the Wind River Indian Reservation are tribal land.

Winter closes most of Yellowstone to cars. Most park roads close to regular vehicles from early November to late April (the 2026 closure began November 1), while the road from the North Entrance at Gardiner, Montana, through Mammoth Hot Springs to Cooke City stays open all year, conditions permitting. The Beartooth Highway east of Cooke City is closed from late fall to spring. Hot Springs State Park at Thermopolis is reached by U.S. 20 through Wind River Canyon and is open year-round.