I were took the Denver - Seattle trip 3 times 2 years ago.(Seattle - (i-90) - (i-82e) - (i-84e)- (i-80e) via Boise,IH and SLC,UT, Cheyenne and Denver) The road are easy without much diffcult.

I'll take another trip from Seattle to Bentonville,AR later this month & this time I'll take Seattle -(i-90)- Billings, MT -( i-25 south), Cheyenne & Denver etc. to see the diffrence.

Good luck

Henry