western section of the great North American Cordillera, W United States and W Canada, stretching from SW Alaska to S Calif. It is composed of a central lowland region (Central Valley, Willamette valley, Puget Sound lowlands) flanked by the Coast Ranges on the west and the Sierra Nevada , Cascade Range , Coast Mountains ., and Alaska Range on the east. Another common reference to the geographical area is, more simply, the Pacific Mountains and Valleys.
