Pacific Margin, 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.
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