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Which lowland regions lie between the Coast Ranges and the Cascade Range or Sierra Nevada?

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Pacific mountain system Coast Mountains along the Torres Channel, an arm of Atlin Lake, northwestern British Columbia, Canada.

The lowland regions situated between the Pacific Coast Ranges and the Cascade Range or Sierra Nevada are known as the Troughs of the Coastal Margin. These extensive plains include the following areas from north to south:1

Puget Sound Lowland: Located in Washington, this region is a half-drowned basin that stretches southward from Canada.12
Willamette Valley: Situated in Oregon, this 30-mile-wide valley lies between the Cascade Range to the east and the Coast Ranges to the west.32
Central Valley: Located in California, this large basin is enclosed by the Sierra Nevada to the east and the Coast Ranges to the west.42

These valleys serve as the primary centers of population and economic activity for much of the U.S. West Coast due to their accessible terrain and fertile soils.1