Mountain range, western U.S. A continuation of the Sierra Nevada , it extends north from Mount Lassen in northeastern California across Oregon and Washington for 700 mi (1,100 km).
Its highest elevation is Mount Rainier . Some of the summits, including Mount St. Helens , have erupted in the recent past. The Lewis and Clark Expedition passed through the range in the Columbia River Gorge. Its northern continuation in British Columbia is known as the Coast Mountains. See also North Cascades National Park .