Campground info, both routes:
1. through Yellowstone to Cody: Buffalo Bill State Park is on the way to Cody. two campgrounds. one where the river flows into the lake and the other one closer to town and on the lake. Both have some elec and water and dump station.
2. through Riverton:
north of town, Wind River Canyon, two campgrounds just below the dam. very scenic. Boysen State Park. or further north at Thermopolis, another state park with mineral hot waters, etc. In Cody, if you want an RV park, there are two big ones. Absaroka Bay RV park and Ponderosa RV park. both good. But busy, so call ahead.