Yellowstone National Park is located in Park and Teton counties in Wyoming, Gallatin and Park counties in Montana and Fremont County in Idaho, United States. It in the oldest national park in the U.S., created in 1872. The park protects geothermal areas that contain about half the world's active geysers and the largest concentration of wildlife in the lower 48 states.
As stated in the foundation document:
Yellowstone National Park, the world’s first national park, was set aside as a public pleasuring ground to share the geothermal wonders and preserve and protect the scenery, cultural heritage, wildlife, and geologic and ecological systems and processes in their natural condition, for the benefit and enjoyment of present and future generations.