My suggestion, even if a bit off route, Hell's Canyon..

It's in NE Oregon... it's one of those places little known outside of Oregon and has incredible scenery and few tourists. (at least there were few the last time I was there... about 3 years ago).

I have suggested Hell's Canyon to several people and all reported to me it was well worth it, some even felt it the highlight of their trip. - JamesJM

P.S. It actually is well known to motorcyclists as the ride is one of the best in the USA.