Thermopolis Boardwalk Trail

The Thermopolis Boardwalk Trail loops through the heart of Hot Springs State Park, home to what is recognized as the world's largest mineral hot spring. The Big Spring releases approximately 8,000 gallons per minute of mineral-rich water at a constant 135 degrees Fahrenheit, creating a perpetual cloud of steam that drifts dramatically across the landscape in cooler weather and gives the park an otherworldly atmosphere throughout the year.

The boardwalk passes directly alongside the vivid mineral terraces that the spring has built up over centuries, with brilliant orange, yellow, and white travertine formations coloring the landscape. The water flows across these terraces in shallow, steaming channels before cascading into the Bighorn River below. The colors are produced by thermophilic bacteria and algae that thrive in the hot mineral water, creating living paintings of extraordinary vividness.

The Wyoming State Bath House at the park's center offers free soaking in the mineral waters, making this trail the rare hike that can end with a therapeutic soak. Interpretive signs along the boardwalk explain the geology, chemistry, and Native American cultural significance of the spring, which the Shoshone and Arapaho peoples ceded to the federal government in 1896 on the condition that it remain free and open to all people forever. This remarkable provision is still honored today.