1,036,311,821 visitors served.

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.

Geography and wildlife The plateau lies at an average 2,440 m/8,000 ft above sea level and is an area of radial drainage; parks forming the reserve extend down valleys on both sides of the Rocky Mountains. Geologically the region is of recent volcanic origin, a caldera formed by an eruption about 600,000 years ago. It is an area of intense hydrothermal activity, containing more than half the geysers of the world, mud pots of acid-dissolved minerals, steam-spouting fumeroles, and hot springs. Old Faithful throws steam and water to a height of up to 52 m/170ft at intervals of 37 to 93 minutes. The highest geyser is the Giant, with a hot-water jet over 60 m/200 ft high; and the lengthiest eruptions come from the Giantess, lasting for over four hours, twice a year. Other natural phenomena include petrified forests, brilliantly-coloured rock formations, mud volcanoes, and cones and terraces created by mineral deposits from the hot springs. Sites include Mammoth Hot Springs, with terraces up to 90 m/300 ft high.

The Yellowstone River flows through Yellowstone Lake and the Grand Canyon of Yellowstone. The park is heavily forested, mainly with conifers; fires are an essential part of the forest's natural ecocycle, clearing old trees to allow for new growth.

Large herds of bull moose, elk, antelope, and bison roam the region. Other species include grizzly bear, bighorn sheep, marmot, lynx, and otter.

Albright, Horace Marden Billings

Cody geyser

Idaho Madison River

West Yellowstone Wyoming

Yellowstone (river)