Southwest Washington is a region of Washington.
For our purposes, the Southwest Washington region consists of Cowlitz, Clark, Lewis, Pacific, Skamania, and Wahkiakum counties.
I-5 connects the region to Seattle and Portland. If coming from the Columbia Plateau/Central Washington, take US-12 or SR-4 west. From the Oregon Coast, take US-101 across the Columbia River.
The Amtrak Cascades service stops in Kelso and Vancouver, WA.