This map (thanks Heidi!) shows the setting in north-central Wyoming. Arrows mark locations where river superimposition occurs; edWare3D images of these locales are shown below.
(Click for high res version)
From Boysen Reservoir, the Wind River cuts through the Owl Creek Mountains forming the Wind River Canyon on its way into the Big Horn Basin. So downstream is into the mountains from the Wind River Basin. I've always been disoriented driving through this Canyon. The water looks like it's flowing uphill!
(Click for high res version)
This animation circles Boysen Reservoir. Remember that downstream is into the mountains.
The Wind River becomes the Big Horn River in the Big Horn Basin.
On the west side of the Big Horn Basin, the Shoshone River exits Buffalo Bill Reservoir and cuts the Shoshone River Canyon near Cody, WY. It's incredible that the river doesn't flow slightly south (left in the image) through gentle terrain.
(Click for high res version)
Back along the Big Horn River, here are views of cuts through Sheep Mountain and Little Sheep Mountain. Both these landforms are anticlines - upfolded structures with oldest strata at their cores.
Sheep Mountain (Click for high res version)
Little Sheep Mountain (Click for high res version)
It's only appropriate that the Big Horn River be superimposed where it exits the Basin as well - and it's a spectacular example. Here's Big Horn Lake in Big Horn Canyon along the Big Horn River through the Big Horn Mountains leaving Big Horn Basin. I think I see a naming trend here!
(Click for high res version)
For anyone who's interested in the world's geological wonders, this area is well worth a visit.
I'd be interested to hear about precip changes over that time.