Yellowstone National Park

Oldest US nature reserve, and largest in the lower 48 states, situated on a broad plateau in the Rocky Mountains, chiefly in northwest Wyoming, but also projecting about 3 km/2 mi into southwest Montana and eastern Idaho; area 8,987 sq km/3,469 sq mi. The world's first national park, Yellowstone contains more than 10,000 geothermal features with more than 200 active geysers, including Old Faithful, which erupts about every 80 minutes. Established in 1872, the park is now a World Heritage Site and one of the world's greatest wildlife refuges, with around 50 animal species. In 1988 naturally occurring forest fires burned 36% of the park.

History
John Colter, a trapper, was the first European to explore the area in 1807. At first his reports met with ridicule, but they were later confirmed by others, including Osborne Russell, a trapper in the 1830s, and James Bridger in 1837. The first official survey was made in 1870, and in 1871 Ferdinand Hayden's expedition documented the unique physical geography of the Yellowstone district, leading to its declaration as a national park in 1872.