Nebraska’s Agate Fossil Beds are a National Monument famous as the site where local rancher James Cook and subsequent paleontologists discovered some of the world’s best preserved and most complete fossil evidence of Miocene-era giant mammals such as the Menoceras of the rhinoceros family, Moropus, a distant relative of the horse, and Dinohyus, also known as the “terrible pig.”



The National Monument’s Visitor Center offers a 12-minute introductory film to the area and its history, as well as two exhibit galleries. The first exhibit showcases lif- sized replicas of the animals found fossilized in the hills beyond the visitor center. Smaller displays feature both real and replica fossils found in the area, including a replica of the watering hole “bone bed” from which most of the fossils were found.

The James Cook Collection gallery features cultural artifacts of the Lakota dating to the late 1800’s and early 1900’s. Many of the items belonged to Cook himself, who, as the owner of Agate Springs Ranch, developed a trading relationship and personal friendship with the chief of the Oglala Lakota, Red Cloud. Highlights of the collection include a whetstone belonging to Crazy Horse, weapons, suits and headdresses belonging to American Horse, and Red Cloud’s moccasins and pipe.


The park is home to two hiking trails, both of which lead to sites along the Niobrara River where James Cook uncovered fossil evidence from his quarries in the late 1800’s. The 1.6 mile Daemonelix trail at the park’s west end takes guests past several in-site fossil exhibits, including the petrified remnants of tunnels once inhabited by the paleocastor, or dry land beaver, who lived in the area in burrows, much like the present day Prairie Dog. The name Daemonelix, or Devil’s Corkscrew, refers to the shape of the burrows dug by the Oligocene period mammals. At the trail’s highest point, visitors enjoy a view of the vast plateaus east of the Rocky Mountains that form the northern High Plains.

The 2.7-mile Fossil Hills trail is a paved, wheelchair accessible trail that begins at the visitor center. The trail crosses the Niobrara River and surrounding wetlands and passes behind Carnegie Hill and University Hill, before looping back to the Visitor Center through plains of mixed-grass and short prairie. Along the trail, guests can walk up to the hillside sites where James Cook made most of his fossil discoveries in the 1880’s. There is also a short trail that leads to the Harold Cook homestead cabin, which has been restored to its 1910 appearance.



History: The Agate Fossil Beds site holds a history that dates back 20 million years to the Miocene epoch, as seen through the fossils found there. The evidence of large mammals is among the best-preserved and complete collection of such fossils in the world.

The National Monument gets its name from the Agate Springs Ranch, which was purchased by James Cook from his father in law in the late 1800’s. James Cook was a cowboy and rancher who had developed a close friendship with OC Marsh, a paleontologist from Yale, who spurned his interest in fossils. On one visit to his future father-in-law’s ranch in Nebraska, he discovered some fossils. After purchasing the ranch, he would frequently invite paleontologists to stay with him while conducting further digs in the area. It was on one such visit that the group confirmed the world famous 20 million year old bone bed located in the University and Carnegie Hills.

James Cook’s son Harold, grew to be a highly respected self-educated paleontologist, and continued inviting other scientists to work on excavations in the area through the 1920’s. Fossils were collected on behalf of Carnegie Museum, Yale University, the University of Nebraska and Amherst College. Harold lived nearby at the Bone Cabin Complex, referred to now as the Harold Cook Homestead. The cabin was listed on the National Register of Historic Places in 1977. The Agate Fossil Beds National Monument was established in 1997, many years after being approved by Congress in 1965.

The descendants of the Cook family still own the ranch, and have donated the items in the James Cook Collection to the National Parks Service with the commitment that they remain within the vicinity of the Cook family home.

Ongoing Programs and Education: Park Rangers bring fossil kits to area classrooms and give talks on the history of Miocene Mammals and the Agate Fossil Beds National Monument. Programs on site include activities at the Visitor Center that contribute to completion of the Junior Ranger badge.

301 River Road Harrison, NE 69346, Phone: 308-665-4113

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