Colter’s Hell is a large, mostly extinct geyser basin along the Shoshone River, with a few hot springs, vents releasing sulphurous gasses, some of the world’s largest extinct geyser cones, and thermal pools, and although about 170 acres of this thermal area are listed on the National Register of Historic Places near these historic markers, the area actually covers several square miles. It was named for John Colter, a hunter with the Lewis and Clark Expedition of 1804-1806, whose later descriptions of the volcanic region were met with such disbelief that others called it Colter’s Hell. Afterward, Colter and expedition interpreter George Drouillard entered the wild, unknown Yellowstone region seeking trading contacts with Crow Indians while representing Manual Lisa’s St. Louis Fur Company from Ft. Raymond on the Big Horn River in Montana in October 1806. Information from their 1807-1809 treks produced descriptions and comprehensive maps of the Big Horn basin, including Cody. In 1807, Colter entered the Big Horn Basin by way of the old Crow Indian trail through the Pryor Gap following the Stinking Water, now the Shoshone River, and at this site he encountered a still active geyser basin and observed sulphurous boiling water pouring into the river. The geothermal area held special spiritual significance for Indians, who placed stone circles and petroglyphs nearby, and both historic and prehistoric Indians frequented the area for the medicinal qualities of its mineral waters.