Glad you’re comin’ out our way, pilgrim! Hope you have a good time while you’re here. I live about 75 miles east of Cody, and about 35 miles north of Thermopolis - allow me to present dono’s Wyoming travelogue:
You’ll have two choices leaving Cody - US 14 going east, or WYO 120 going southeast. These are both two-lane roads, and the speed limit is only 65 - you won’t get to a 75 MPH freeway until you hit I-25.
If you take US 14, you’ll go through some colorful badlands and have a good opportunity to see some of the McCullough Peaks wild horse herd from the highway. Then you’ll have two choices to go over the Bighorn Mountains, and meet I-25 in either Sheridan or Buffalo. Either route is very scenic - the northern route probably more so. You’ll climb some of the most pucker-inducing switchbacks that I’ve driven, and go right past the Medicine Wheel. The Wheel requires a short sidetrip and a bit of a hike, but it’s worth it. If you go the southern route to Buffalo, it’s still a pretty drive over the Bighorns, and you’ll go right through my town (I’d be honored to buy ya’ a beer or two.)
If you take WYO 120 you’ll go through Thermopolis, home of “The World’s Largest Mineral Hot Springs” (which, since the flow is down, I don’t think is true any longer.) There are two commercial pools with water slides, and a free bathhouse run by the State - when Chief Washakie gave the springs to the white man, he stipulated that part of the springs would always be for the free use of the people. There’s a State park with a free-roaming buffalo herd. Thermopolis also has a dinosaur quarry and museum. Since it’s a private quarry, you can even arrange to participate in digs. Thermop sits in red-rock country and is a nice little town. It’s really worth a night’s stay, but since it’s only 80 miles out of Cody, you might not want to do that. But OTOH, you can still make Thermop to Denver in a day, easy. When you leave Thermop, you’ll go through the Wind River Canyon in the Owl Creek Mountains (pretty) and wind up in Shoshoni. In Shoshoni, be sure to stop at Yellowstone Drug for a World-Famous Milkshake (trust me on this one.)
Whichever way you go, once you get to Sheridan, Buffalo, or Shoshoni, the country turns pretty much as described by previous posters - flat, dry, and windswept. There are some famous Indian Wars battlefields to see around Sheridan, but that’s about it. It’s ground you’ll want to cover as quickly as possible. (We call the stretch between Shoshoni and Casper “The Void”.)
Both routes go to Casper, where you’ll have two choices: You can stay on I-25 and go to Denver via Cheyenne, or you can take the back roads and go WYO 220 - 497 - US 287 and go to Denver via Laramie. There’s not much difference in time, and not much to see either way. Laramie is a college town and presumably there’s some fum stuff to do there (so my daughter tells me, anyway :rolleyes: ) but I’ve never spent much time there. The drive from Laramie to Ft. Collins is pretty, though.
Hope this helps! If I can provide any more information on the smaller attractions along the way, let me know! (By coincidence, my Field Office just dedicated a new visitor’s center at a dinosaur tracksite today - it’s right off the road to Sheridan.)