National preserve in northwestern Wyoming, southern Montana, and eastern Idaho, U.S. The oldest national park in the U.S. (and in the world), it was established by the U.S. Congress in 1872; it covers 3,468 sq mi (8,983 sq km).
The Gallatin Range, Absaroka Range , Snow Mountains, and Teton Range extend into it. Yellowstone has unusual geologic features, including fossil forests and eroded basaltic lava flows. It also has 10,000 hot springs, which erupt as steam vents, fumaroles, and geysers. Old Faithful, the park's most famous geyser, erupts every 33 to 93 minutes. It has many lakes and rivers, including Yellowstone Lake , Shoshone Lake, the Snake River , and the Yellowstone River . In 1988 an extensive series of forest fires laid waste to large areas of the park.