Can you define what western and eastern parts are specifically please? 
This person's question was never answered. I'd be interested to find out the answer to this myself.
Well tbh it's pretty self-evident given the geography no? The Cascades are about the starkest dividing line in any state.
True, but I think they were wanting to know precisely which counties the OP of this thread used to make their designation.
Ftr, it is almost certainly all counties east of and including: Klickitat, Yakima, Kittitas, Chelan, and Okanagon. The map on the Wikipedia page for Lincoln (state) shows it accurately.
