For our purposes, the Southwest Washington region consists of Cowlitz, Clark, Lewis, Pacific, Skamania, and Wahkiakum counties.
Portland International Airport (IATA: PDX)is quite convienient for this region, being just across the river from Vancouver (Washington): see the Portland article for details. Flights to many major US airports and a few international connections.
Seattle International Airport (IATA: SEA)is located about 2 hours north of Kelso: see the Seattlearticle for details. Greater number of international flights than Portland.
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.