Hagerman Fossil Bed, Idaho
This spot has the distinction of being one of the most fossiliferous Pliocene-aged sites (5 to 1.8 million years old) in the world due to the fact that approximately 3,000 new fossils are found each year from animals that lived between 2.4 and 5.4 million years ago [source: Idaho Tourism]. It is also home to Idaho's state fossil: the Hagerman horse (Equus simplicidens), which is considered to be the evolutionary link between the modern horse and its prehistoric predecessor. In fact, the site contains the largest concentration of these fossils in North America and is considered one of the top six most important sites in the world regarding the fossil history of horses [sources: Idaho Tourism; National Park Service].
The visitors center has an instructional DVD and a variety of fossils on display because the Hagerman site is not only full of horse fossils, but is also considered to have the world's richest late Pliocene Epoch deposits with more than 220 species of plants and animals [source: National Park Service]. Regular events allow visitors to go out on digs and help paleontologists unearth new discoveries.