It appears the only others are:
Lac Qui Parle, MN (2)
Lincoln, MN (2)
Big Stone, MN (1)
Buffalo, SD (2)
Wow. Only 12 in the whole country. Buffalo (SD) is surprising since it's extremely poor.
In WA, that would be Mason, Pierce, and Thurston counties, which are all in the South Sound. Sounds about right. There are quite a few conservative Democrats in that region.
You could also add Jefferson and Cowlitz, I guess, though Reagan only won them in 1980 (and primarily because of Anderson).
All voted for Nixon in 1972.