YELLOWSTONE NATIONAL PARK, a national Ameri can public park, the first and most noted of a number of such national reserves set apart by the U.S. Government to preserve, for the benefit and enjoyment of the people, certain regions of extraordinary or unique natural grandeur and impressiveness. Yellowstone National Park includes about 3,35o sq.m.-62 m. long and 54 m. wide—lying largely in the north-west corner of Wyoming but extending a little over 2 m. northward into Montana. National forests surround the park on all sides—the Gallatin, Absaroka and Beartooth to the northward ; the Shoshone to the eastward ; the Teton and Targhee to the southward ; and the Targhee, Madison, and Gallatin to the westward.
A broad volcanic plateau with an average elevation of 8,000 ft. occupies the centre of the park. The park is enclosed on its northern and north-western border by the Gallatin range, a bold picturesque sierra of which Electric peak, elevation i 1,000 ft., constitutes the culminating crest. The Teton range, one of the most spectacular features of the northern Rockies, looms high upon the southern horizon, but only its bold spurs and foot-hills enter the park. East of the Tetons stretch the wild Gros Ventre and Wind river ranges well up toward the southern boundary of the park. The majestic Absaroka range, connected at the south with the Wind river range, forms an unbroken barrier along the whole eastern side of the park, its western side and many of its rugged peaks and canyon-grooved mountain masses lying within the park. A confused mass of mountains near the north-eastern part of the park connects the Absaroka with the Snowy range. The general high elevation of the park is reflected in the climate, the mean annual temperature being considerably lower than that of the surrounding lower areas, and the amount of precipitation, both rainfall and snowfall, higher. At the Yellowstone Park weather station, elevation 6,200 ft., the mean temperature for the year is 38.7° F, ranging from 18.0° F in January to 61.3° F in July. The average annual snowfall at the Yellowstone Park sta tion has been 100.5 in., varying from traces in July and August to 20.6 in. in January. The mean relative humidity varies from 53% at noon to 75% at 6 A.M. The annual percentage of sunshine is 56.
Such climatic conditions favour forest development and the growth of luxuriant grasses together with a varied alpine verdure. The whole of the park lies within the limits of the lodge-pole pine forest characteristic of the high Rockies though the higher slopes of the Absarokas and other high ranges are clothed with belts of spruce-fir forests and the crests of the mountains themselves are above timber line. The lodge-pole pine is a pioneer tree which invades terrain left open by other species, chiefly as the result of forest fires. Sunny, rocky slopes are in places occupied by the Douglas fir. Aspen and Engelmann spruce and a few limber pines are intermingled with the lodge-pole pines. Beautiful intermon tane meadows where numerous grasses and sedges carpet the ground, and saxifrages, valerians, cinquefoils, senecios, orchises, betonies, gentians, grass of Parnassus and many other brilliant flowers blossom during the summer are interspersed with the rocky forest-clad ridges, while the banks of many pools, lakes and streams abound in water-lilies, buttercups, cresses, reeds and rushes. A few salt-loving plants grow about the hot springs and geysers, while in the hot waters issuing from them an interesting series of low plant forms is found.
The native fauna of the park area has been jealously guarded and preserved. Many elk and deer, a few antelope, bison, moose and mountain sheep ; bears, foxes, coyotes, even wolves, lynxes and panthers; many species of squirrels, ground squirrels, mice, shrews, gophers, rabbits; the beaver, muskrat, otter, marten, skunk, weasel, badger, wolverene, marmot, mink; and several others less common wander in larger or fewer numbers into or about the park, though most of them may be encountered only in the remoter, less frequently visited, sections of the park. Pro portionally as richly numerous and varied as the mammal life, the bird forms include over 200 species, some permanently resident, many only migrant. The streams are well stocked with fish, particularly trout, of which the native redthroat (Salino clarkii) is one of the gamest and most eagerly sought.