Yellowstone National Park, a nature and wildlife preserve in the western United States. It is the oldest national park and until 1980 was the largest. Yellowstone lies in the Rocky Mountains, largely in Wyoming but also in Idaho and Montana. The park consists mostly of plateaus and mountain ranges at elevations varying from roughly 5,300 to 11,300 feet (1,600 to 3,400 m) above sea level. The area of the park is 3,468 square miles (8,982 km 2 ).
The park is an awesome region of wilderness, mountains, geysers, hot springs, lakes, canyons, and rivers. It attracts several million visitors yearly. Yellowstone takes its name from the yellow canyon walls of the rushing Yellowstone River.
Snow-clad ranges within the park include the Absaroka and Gallatin ranges; the Tetons rise majestically just south of Yellowstone in Grand Teton National Park. Yellowstone's surface features are primarily of volcanic origin. Glaciers and running water have also left their imprints on the land through erosion.
Yellowstone's world-famed geysers indicate that volcanic action continues close to the earth's surface. The geysers lie chiefly in thermal basins in the southwestern part of the park. Some geysers erupt at fairly predictable intervals. Old Faithful expels a jet more than 100 feet (30 m) into the air about every 77 minutes on the average. When Giant Geyser erupts, it hurls water about 250 feet (80 m) overhead.
Norris Geyser Basin is the most active thermal area in the park. At Mammoth Hot Springs, near the north entrance to the park, steaming water flows over travertine terraces vividly colored by algae. The Fountain Paint Pot area, in the Lower Geyser Basin, has a wide variety of geysers and hot springs in a small area.
Yellowstone Lake lies 7,733 feet (2,357 m) above sea level and covers 139 square miles (360 km 2 ). Other large lakes are Heart, Lewis, and Shoshone. Within the park are the headwaters of the Snake, Madison, Gallatin, and Yellowstone rivers. The Yellowstone plunges down many waterfalls. Its Lower Falls drops 308 feet (94 m), nearly twice the height of Niagara. Upper Falls drops 109 feet (33 m) and Tower Falls on Tower Creek 132 feet (40 m).
The most spectacular of the many canyons is the Grand Canyon of the Yellowstone River. It extends about 15 miles (24 km) downstream below Upper Falls, between walls 1,200 feet (370 m) high.
High mountain summits rise beyond the timber line. On the slopes and plateaus stand evergreen trees, chiefly pine, spruce, fir, and juniper. Aspen, cottonwood, alder, and willow turn bright in the autumn. Petrified trees lie in the northern area.
Animals are protected by law; only park rangers may carry guns. Black bears frequent the highways looking for handouts of food. Though they seem friendly and clown-like, they are dangerous. Visitors are warned not to feed them and to watch them from a distance. Also found in the park are grizzly bears, deer, elk, bison, pronghorn, bighorn, coyote, bobcats, and moose. Gray wolves, which by the 1940's had been virtually eliminated from the park, were reintroduced into Yellowstone in 1995.
Trout are plentiful. The park issues fishing permits, and visitors may rent boats and tackle. The more than 200 species of birds include ducks, geese, gulls, pelicans, cormorants, swans, ospreys, and eagles.
The official park season is usually from May 1 to October 1, with all roads and facilities, including hotels, cabins, and campgrounds, open from June through September. Only a few roads and facilities are open during winter, when the park is bitterly cold and engulfed in deep snow.
Ranger naturalists explain the wildlife, geysers, and other natural phenomena. There are several museums and other exhibits. Foot and bridle trails thread the park. There are about 300 miles (480 km) of public roads. The superintendent's headquarters are at Mammoth Hot Springs.
The first white man to see what is now Yellowstone National Park was probably John Colter, who entered it on foot and alone in 1807. Congress established the area as a national park in 1872. The advent of automobiles in the 20th century brought crowds of touring motorists, and Yellowstone became one of the nation's most popular parks. A severe earthquake in 1959 opened new hot springs. In 1988, during one of the driest summers in decades, fires burned nearly half of the park's lands.