Harris traces the remarkable post-expedition career of John Colter, the private who received permission to leave the Corps of Discovery in 1806 to join a trapping party and subsequently became one of the first American mountain men. The article documents Colter’s solo winter journey of 1807-1808 through the Yellowstone region, during which he became the first known Euro-American to witness the geothermal wonders that his contemporaries derisively labeled “Colter’s Hell.” Harris provides a detailed reconstruction of Colter’s famous 1808 escape from the Blackfeet, in which he was stripped naked and forced to run for his life across the Montana prairie, eventually eluding his pursuers by hiding in a beaver dam on the Jefferson River. The article evaluates the various accounts of this episode and places Colter’s adventures in the context of the early Rocky Mountain fur trade that followed in the expedition’s wake.