Hot Springs State Park

Hot Springs State Park sits in Thermopolis, Wyoming, along the Big Horn River, and it holds a distinction that draws visitors from across the country: one of the world’s largest mineral hot springs. Big Spring discharges roughly 1,500 gallons of hot water per minute, with temperatures commonly reported around 127 to 135 degrees Fahrenheit, feeding a series of vivid mineral terraces before cooling into designated pools where the public can bathe for free. That combination of geological spectacle and genuine accessibility, backed by a treaty obligation, makes this one of Wyoming’s most unusual public lands.

The Hot Spring, Terraces, and Rainbow Terrace Walk

Tepee Pool and Spa draws considerable attention, though Star Plunge is temporarily closed and visitors should verify its status before planning around it. The spring itself is worth studying before you soak. The main vent discharges water continuously, and the minerals it carries build up over time into travertine terraces, calcium-carbonate deposits whose colors are shaped by dissolved minerals and communities of thermophilic algae and microorganisms, forming pale orange and white formations that resemble a scaled-down version of Yellowstone’s Mammoth Hot Springs. A short paved walkway called the Rainbow Terrace Walk loops past the most colorful formations and offers clear views of the steam rising from the outflow channels. The colors shift depending on the angle of light and the algae communities living in the warm runoff, so the terrace looks different in morning sun than it does at midday.

The State Bath House

Under an 1896 treaty with the Eastern Shoshone and Northern Arapaho tribes, Wyoming is required to provide free public access to the hot spring waters. The State Bath House honors that obligation with no-cost soaks in indoor and outdoor mineral pools, with changing and locker facilities available for visitors. Soaking is generally limited to 20-minute sessions, and visitors may need to wait during busy periods, so plan to arrive early on summer weekends. No reservation is needed, and there is no charge.

Tepee Pool and Spa operates adjacent to the state bath house for visitors who want more amenities or extended soaking time, and carries its own admission fees separate from the state park. Star Plunge, a waterslide and mineral-pool facility also located nearby, is temporarily closed pending resolution of an ongoing management and legal dispute; visitors should confirm its status before planning a visit around it.

Bison Range and River Corridor

The park maintains a resident bison herd in a large enclosure along the Big Horn River. Visitors can view the bison from the park road through the pasture and should remain in their vehicles while in the bison range. Animals can weigh over a ton, and calves are typically visible in spring, with the herd active throughout the day. The river corridor itself supports cottonwood stands and a variety of birds, including great blue herons and several species of waterfowl. Fishing is permitted in the Big Horn River adjacent to the park, and the cottonwood floodplain makes for a pleasant walk even outside of fishing season.

Pet Policy

Pets are welcome in Hot Springs State Park and must be kept on a leash no longer than 10 feet and physically controlled at all times. Pets are not permitted inside the State Bath House or in the water of any thermal pool. Keep pets away from the bison range fencing, as the animals can react aggressively to dogs. Clean up after your pet and dispose of waste in the trash receptacles provided throughout the park.

Wildlife to Be Aware Of

The bison herd is the most significant wildlife consideration in the park. These animals look calm but can move quickly and without warning. When visiting the bison pasture, view bison only from inside your vehicle, never approach bison or calves, and obey all posted closures and barriers. Never approach calves under any circumstances, as cows with young are especially unpredictable. Do not feed bison or attempt to attract their attention, and do not startle them by making sudden movements or loud noises near the fence line.

Rattlesnakes are present in rocky and brushy areas along the trails, particularly in the drier sections away from the river. Watch where you step when moving through tall grass or along rocky outcrops, and never reach into crevices or under ledges without looking first. Most rattlesnake encounters end without incident if the snake is given space to move away.

The thermal features outside the designated pools carry a serious scalding risk. The spring water emerges at temperatures that can reach 135 degrees and cools gradually through the outflow channels, but water that looks still and approachable can still be hot enough to cause severe burns. Do not wade in, touch, or let children approach the open thermal channels or natural pool edges. Stay on the designated walkways near the terraces and observe all posted barriers.

Practical Information

Hot Springs State Park is located at 220 Park Street in Thermopolis, Wyoming, in Hot Springs County. Thermopolis is the nearest town and offers lodging, dining, and fuel. The park is accessible from U.S. Highway 20, which connects south to Shoshoni and north toward Cody. From Casper, the drive is approximately two hours north on U.S. 20/26 to Shoshoni, then north on U.S. 20 into Thermopolis.

There is no entry fee for the park. Access to the State Bath House mineral pools is free to all visitors, honoring the terms of an 1896 treaty with the Shoshone and Arapaho tribes. The State Bath House is open year-round, though hours vary seasonally. The park itself is open daily. No reservations are required for general park access or the free bath house. The bison range and terrace walk are accessible throughout the year, and the mineral pools are especially popular in winter when the warm water is most appealing against cold outside temperatures.