top of page


Agate Fossil Beds National Monument, located in Harrison, Nebraska, first opened its

visitor center to the public back on June 14, 1997; however, its history long

predates this establishment. The park was first authorized in June 1965, on a property 

formerly known as Agate Springs Ranch. Even before the park's authorization, the

Fossil Hills (formerly the Agate Springs Quarries) offered astounding remains of

prehistoric life that eventually put the property on the map. The Harold J. Cook

Homestead, now known as the Bone Cabin, became a lab site for paleontologists,

and was listed on the National Register of Historic Places in 1977. This homestead

                                                                 was a functioning cattle ranch owned by
                                                                 Captain James Cook (not the same as the 

                                                                 famous British naturalist) who befriended the 

                                                                 Oglala Lakota and Northern Cheyenne tribes, who would  

                                                                 exchange gifts while travelling between reservations to temporary 

                                                                 settlements on the Agate Springs Ranch. As a result, over 500 Native American

                                                                 artifacts have been collected and are on display in the local museum.

                                                                 This friendship existed as far back as 1874, long before Mr. Cook moved to the ranch.                                                                            


The vast collection of ancient mammal bones became the focal point of the establishment and put itself on the map as one of the most productive fossil bearing locations not only in North America but also on the entire planet. Scores of fossils have been discovered many of which are nearly complete and in exquisite preservation. This was likely due to the unique taphonomic conditions of the locality; the valley was once filled with ephemeral waterholes, bringing herds of extinct wildlife together during periods of drought, numerous species eventually succumbing to dehydration and exposure. The Agate Fossil Beds National Monument is an NPS site due to this area being the only place one can find such Miocene animals in their entirety, in abundance, and in such good condition.


Dating to the beginning of the Miocene between 23 and 16 million years ago, the landscape was warmer than today, ushering in a subtropical climate that featured grassy plains and wooded savannah: biomes unique to North America's geography ​now confided to the American Midwest. This allowed for a menagerie of fauna to coexist almost akin to the Serengeti; ancient mammal lineages such as entelodonts, chalicotheres, oreodonts, protoceratids, and amphicyonids survived alongside the basal ancestors of camels, horses, rhinoceros, and beavers. It was this transitional period in mammalian evolution that defined the Miocene Epoch.

One of the first fossil hunts


Agate Fossil Beds National Monument map

Fossil Assemblage

The Devil's Corkscrew, also known as Daemonelix - 
burrows made by Palaeocastor, an extinct beaver. 

bottom of page