The mountain goat is an even-toed ungulate of the order Artiodactyla and the family Bovidae that includes antelopes, gazelles, and cattle. It belongs to the subfamily Caprinae (goat-antelopes), along with thirty-two other species including true goats, sheep, the chamois, and the musk ox. The mountain goat is the only species in the genus Oreamnos. The name Oreamnos is derived from the Greek term oros (stem ore-) "mountain" (or, alternatively, oreas "mountain nymph") and the word amnos "lamb".
Both male and female mountain goats have beards, short tails, and long black horns, 15–28 cm in length, which contain yearly growth rings. They are protected from the elements by their woolly white double coats. The fine, dense wool of their undercoats is covered by an outer layer of longer, hollow hairs. In spring, mountain goats moult by rubbing against rocks and trees, with the adult bucks (males) shedding their extra wool first and the pregnant does (females) shedding last. In the winter, their coats help them to withstand temperatures as low as −50 °F (−46 °C) and winds of up to 100 mph (160 km/h).
A buck stands about three feet (1 m) at the shoulder to the waist. Male goats also have longer horns and a longer beard than a female does. Mountain goats typically weigh between 100 and 300 lbs (45–136 kg); females are usually 10–30% lighter than males.
The mountain goat's feet are well-suited for climbing steep, rocky slopes, sometimes with pitches of 60 degrees or more, with inner pads that provide traction and cloven hooves that can be spread apart as needed. Also, the tips of their feet have dewclaws that are sharp to keep them from slipping.
The mountain goat inhabits the Rocky Mountains and Cascade Range regions of North America, from northern Washington, Idaho and Montana through British Columbia and Alberta, into the southern Yukon and southeastern Alaska. Its northernmost range is said to be along the northern fringe of the Chugach Mountains in southcentral Alaska. Introduced populations can also be found in such areas as Wyoming, Utah, Nevada, Oregon, Colorado, Texas, South Dakota and the Olympic Peninsula of Washington.
Mountain goats are the largest mammals found in their high-altitude habitats, which reach elevations of 13,000 feet (4,000 m) or more. Although they sometimes descend to sea level in coastal areas, they are primarily an alpine and subalpine species. Throughout the year, the animals usually stay above the tree line, but they will migrate seasonally to higher or lower elevations within that range. Winter migrations to low-elevation mineral licks often take them several or more kilometers through forested areas.