We dashed through about 10 years ago on the way to my brother's in Boise, ID and stayed a night in Cody,WY--the museum there was worth seeing--and then just drove through Yellowstone and saw the geyser fields (stay on the paths!),Old Faithful and the Lodge,the Grand Canyon of the Yellowstone, the Obsidian cliffs and then out through West Yellowstone. My DH and I plan to drive through again sometime next May orJune on way to nephew's HS graduation and hopefully this time be able to spend more than one day! If you are driving West, Mt. Rushmore is well worth the stop and has a nice visitors center and the Badlands were very interesting too.