First Timer To Yellowstone

we've been twice. Not many scenic routes to get there. I would go the fastest route to Denver. I-75, I-24, I-57, I-64, I-70. We stayed at the Fort Collins Co KOA. You can take a day trip to Estes Park from there. Last year there was lots of construction in Denver. If you want to see Albuquerque and Colorado Springs, take I-40 through Oklahoma City and Amarillo. That will add a day to your trip out. If not, from Denver, take I-25 north. In Casper take US26 west to Shoshoni, then north on US20 toward Thermopolis. At Greybull there is a KOA. Hwy 14-16-20 turns west to Cody. Stop in Cody and see the Buffalo Bill Museum. If Yellowstone is booked, we stayed at Yellowstone Valley Inn RV Park. 35 miles from the West Yellowstone entrance. We drove back and forth from the RV park to Yellowstone. You can also drive to see the Tetons from there. From Cody, go back east to Greybull, south on US20 to Worland, then US16 east through the Big Horn Mts. (allow plenty of time) and pickup I-90 in Buffalo. From there you can get to the Black Hills and Bad Lands. Once you have your route we can help with campgrounds. Many campgrounds will be closing in September so I would check their websites for closure dates. Tips:
For mountain driving use your engine retarder or jake brake and or lower gear. Don't ride brakes. Approach descent very slowly. Get fuel more often. We stopped when our fuel gauge was at half. Allow plenty of time between stops to allow for construction and windy mountain roads. Purchase a western mountain atlas or truckers atlas that shows steep grades and truck routes. Wish we were going again!