There are plenty of mammal fossils to be found along your road trip, but the reason to head north for our next stop is that Fossil Butte is home to the largest deposit of freshwater fish fossils in the world [source: Wyoming Tourism]. These fossils, from organisms that lived more than 50 million years ago during the Eocene Epoch, are embedded in the various layers of limestone that descend 100 feet from the top of the butte.
Start your tour at the visitor's center where you can see more than 80 fossils, including a 13-foot crocodile and the largest-known articulated bat, and enjoy demonstrations that show how fossils are prepared. If you are visiting during the summer months, on Fridays and Saturdays between 11 a.m. and 4 p.m., you can hike to the fossil research quarry and help park staff round up fossils. There are also several other hiking trails and some great picnic spots.