Agree with 2Gypsies. From I-90, take hwy l6 from Buffalo to Worland, then hwy l6-20 to Greybull, then hwy14-20 to Cody and continue to the east entrance to Yellowstone. Last year, we stayed several days in Gardiner & visited the northern part of Yellowston, then stayed several days in West Yellowstone to visit the southern part of Yellowstone. Both locations are just outside the park. We camped at Jackson Lake campground to visit Grand Teton N.P. Reservations are definitely needed early if you want to stay within the park. MANY things to see in Yellowstone. Have a great trip.
