Indians had a huge part in the history of Yellowstone. Indirectly, they were the cause of its discovery, and more directly they were responsible for its isolation for almost half a century after the discovery of the geysers, the hot springs, and the canyon and lake. Travelers and explorers routinely avoided the trip to Yellowstone for fear of annihilation by hostile Indians. For two generations the territory that is now the park was visited only by fearless and intrepid trappers. Now you can be fearless.