ParTaxer, that looks like an amazing area but perhaps a bit far north.

Tony to answer your question, we will be traveling on I90 through the state from Seattle to Mt Rushmore. So the Butte, Bozeman, Helena, or Missoula area would make for a good halfway point. I am not opposed to camping a bit off the highway for a beautiful location. My only "requirement" is shore power for the wife.
Thank you in advanced!