Photo #24361 - Auto Tour Routes sign. Interstate #25 travels the same path as Oregon Trail, California Trail, Morman's Pioneer Trail and the Pony Express Trail. All trails are National Historical Auto Tour Routes 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.