Opinion of a geographer: if you make two divisions, the cascade crest should be the division between east and west, but I like the concept of an eastern, central, and west Washington. I can't help but wonder, if you're going to make the divisions though, could that third division be better used to highlight another part of the state with more distinction from the rest than the difference the near east side of the Cascades had from the rest of the eastern state. Eg: east and west and Spokane region is third division? East and West but Seattle metro and the islands get the third division?