Roadside turnout with historic information sign The Jim Bridger Trail 1864 - North of this point is the Jim Bridger Trail. The Devils Backbone, the roughest decent on the trail, situated at the northern edge of the plains the trail drops down into the Whistle Creek Valley. In the spring of 1864 Jim Bridger guided 62 wagons from Fort Casper northwest through the Big Horn Basin to Virginia City Montana. With half of the earth’s geothermal features, Yellowstone holds the planet’s most diverse and intact collection of geysers, hot springs, mudpots, and fumaroles. Its more than 300 geysers make up two thirds of all those found on earth.