There’s no mistaking – Thermopolis has the world’s largest mineral hot springs. Thermopolis should be proud of its hot springs; not only are they among the world’s largest, but quite possibly the friendliest. And, if the hot springs themselves aren’t impressive enough, did we mention there’s a resident herd of wild bison roaming the grounds?

Once a part of the Wind River Indian Reservation (home to Eastern Shoshone and Arapahoe tribes), Chief Washakie sold the hot springs to the U.S. for $60,000 in 1897 with the caveat that a portion of them always be reserved for free public use. A pageant celebrating this exchange is held annually the first full weekend of August. Thermopolis, Greek for “hot city,” eventually took its name from the springs.

Today Hot Springs State Park, the busiest in the Wyoming park system with upwards of 1 million visitors annually, operates the free State Bathhouse (living up to Chief Washakie’s request) while two concessionaires run hot pools complete with water slides, spa facilities and tanning decks. Not surprisingly, each group of pools draws a different clientele. Families make a beeline to the concessionaire pools for the water slides and other amenities, while those who just want a relaxing soak head for the quieter State Bathhouse. In addition to having both an indoor and outdoor soaking pool, the State Bathhouse also offers private tubs where you can control water temperature with the flick of a faucet.

All of the pools in the park get their water from the same source though: rain falling on the nearby Owl Creek Mountains enters porous rock layers and moves slowly downward, picking up heat and minerals from the rock as it goes. Hot gases eventually force the water up through crevices and into the Big Spring in the state park. Daily, 3.6 million
gallons of this mineral-rich (sodium, zinc, titanium, magnesium, bicarbonate, among others), 127-degree water – don’t worry, it’s cooled before it reaches the soaking pools – flows through the Big Spring and into the various pools, Jacuzzis, saunas and steam rooms. Most of the bathing pools are kept at around 104 degrees.