John Colter, immortalized on this map in the phrase “Colter’s Route” at top center, was the first European to explore the terrain shown here, part of which is now Yellowstone National Park. Colter was a Corps of Discovery member who went on to make a name for himself as a mountain man and beaver trapper. The exploits he claimed included outrunning and outswimming a group of Blackfoot Indians bent on killing him. In 1810, Colter shared his findings about such features as “boiling springs” and a “stinking river”—in a thermally active area near present-day Cody, Wyoming, that became known as “Colter’s Hell”—with Clark, who added this information to his map.