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This is a ground squirrel (chipmunks have stripes on their cheeks). It looks like a Cascade Ground Squirrel (grey belly), however, based on your location, Golden Mantled Ground Squirrel seems more likely (but their belly is usually cream).
Chipmunks have cheek stripes, ground squirrels don't.
Chipmunks have cheek stripes, not ground squirrels. Based on your location, I think this is a Townsend's Chipmunk