There are several RV parks in West Yellowstone, MT (just outside the West entrance to Yellowstone Park), and several in the Jackson (Hole) area near the Tetons. Many are open year round to accommodate skiers. Check out the Trailer Life RV Directory in these two towns. Like several said above, the weather may be an issue in driving and towing this late in the year. We were in both locations one month ago and the weather was good. The average elevation was 5K feet, so expect it to be cold.