There have been reports, mostly second-hand, of some feral hogs in the Wynoochie (SP?) Valley area, of Grays Harbor County, up north of Montesano. I lived for quite a few years in the general area ( Matlock ) and never heard any first-hand reports.
Having said that, I gotta say that it would be an ideal location for them to thrive, lots of succulant plants, farmers fields, fruit trees, thick undergrowth to hide in, mild winters, cool/ moist summers.
Mark