Casper WY to SLC via Fish Haven ID

Not sure if you're looking to camp there, but the Bear Lake State Park on the Idaho side has a pretty decent CG. A few sites have electric hookups. There is also a KOA in Garden City, Utah (not far from Fish Haven) and a Utah version of Bear Lake SP on the south end of the lake. Not sure what that one's like, as we didn't drive thru it.

Also if you take the route to Rawlins you could stop at Martins Cove just past Devel's Gate just south of Casper. Someone from your part of the country might be interested this. It gets lots of visitors every summer. The Cove is where about 100 Mormon pioneers perished from winter storms while they holed up on their way to SLC. An old Western ranch with log cabins and buildings was built near the site and is the start of the free guided tours.

If you don't have any reason to go to Lander, then the route the previous poster said is a good way. Take off I-80 onto 30 just past Green river and Little America headed to Kemmerer. Continue on 30 for approximately 24 mi., then turn left onto 89/30. About another 4-5 mi. you come to another junction, you will continue west to Laketown, Garden City and Fish Haven on Bear Lake. The lake is a beautiful turquoise.

Happy Trails

South Pass is a pretty hard pull coming up out of Lander! A suggestion: Casper to Rawlins, I 80 west to SLC. Although, Parleys Canyon is a pretty good pull also. Once in Utah, you could go north to Ogden at Coalville and avoid Parleys, it it would add some length to your trip to SLC