Glacier National Park, a unit of the National Park System in the Rocky Mountains of northwestern Montana. The park's rugged terrain was carved mainly by glaciers during the last Ice Age. About 50 small glaciers remain; all are nestled high in the mountains. Other features include jagged peaks and knife-edged ridges, deep U-shaped valleys, and sparkling clear lakes and streams. Lake McDonald and St. Mary Lake are the largest of the park's more than 200 lakes.

Magnificent virgin forests occur in Glacier National Park, especially on the western mountain slopes, which face the inflow of moist Pacific air. Evergreens, including various kinds of pine, spruce, fir, hemlock, and larch, predominate. Deciduous trees, including colorful quaking aspen, also grow within the park, and wildflowers are found in great variety. Only such hardy plants as mosses and lichens grow in the alpine tundra above the timberline.

Nearly every kind of large mammal native to the United States—including moose, elk, bears, cougars, mountain sheep, and white-tailed deer—roams the park. Among the 200 species of birds are golden and bald eagles ptarmigan, and osprey.

The park season is usually June 15 to September 15. Visitors may drive through the park on Going-to-the-Sun Road, which runs between West Glacier and St. Mary, Montana, crossing the Continental Divide at Logan Pass at about 6,650 feet (2,027 m) above sea level. Within the park are numerous hotels, motels, campsites, and trailside chalets. There are more than 700 miles (1,130 km) of trails for horseback riding and hiking.

Glacier National Park was established in 1910. In 1932 it was united with the adjoining Waterton Lakes National Park in Alberta, Canada, to form Waterton-Glacier International Peace Park.