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Black Hills Parks & Forests Association

Agate Fossil Beds’ Ancient Wonders: Discovering Giants In the Hills

Giants beneath the Agate hills

A pair of low grass hills rises above the Niobrara River in the far western corner of Nebraska, and they look like nothing in particular. Inside them lie some of the most complete records of Miocene mammals found anywhere in North America. Agate Fossil Beds National Monument protects those hills, the quarries cut into them, and the prairie that has changed little since the animals in the rock were alive.

People come to Agate for two very different reasons, and both are worth the drive. The fossil hills hold whole skeletons of animals that scientists elsewhere know only from scraps. The visitor center holds the Cook Collection, a group of Lakota objects that came to a local ranching family through a friendship with Chief Red Cloud and other Oglala Lakota leaders. This page follows the fossils. The monument itself ties the two stories together on the ground.

Agate is one of four sites in the Black Hills and western Nebraska where Black Hills Parks and Forests Association serves as the nonprofit cooperating association. The National Park Service runs the monument. We help tell its stories.

Where
W. Nebraska
34 mi north of Scottsbluff, off Hwy 29
Fossil age
~20M yrs
early Miocene epoch
Set aside
1965
a national monument
Entrance fee
Free
no entrance or use fees
Trails
2
1 mi and 2.8 mi loops
Managed by
NPS
BHPFA partner site

By Jason Gray, Black Hills Parks & Forests Association

A window into the Miocene

Roughly 20 million years ago, the country around Agate was warmer and wetter than the short-grass prairie you see today. Woodlands and open savanna spread across the plains, watered by streams that fed into slow rivers. Grasses were still spreading, and the animals that grazed and browsed here belong to a world that no longer exists.

What makes the Agate beds so useful to science is not that they hold fossils. Many places do. It is that they hold so many animals together, and so complete. Most fossil sites yield a jaw here, a legbone there. The main quarries at Agate held bones packed by the thousands, whole skeletons among them, all from the same short slice of time.

One long-standing explanation is a drought. As water dried up across the plains, animals crowded toward the last shrinking waterholes, and many died there. Their bodies gathered in the mud, were buried, and slowly turned to stone. Whether or not every detail holds up, the result is a rare, crowded snapshot of a single Miocene community, which is why researchers still work the site.

The animals of the fossil hills

The quarries at Agate have produced a short cast of memorable animals. None of them would look quite familiar today, and a couple would stop you in your tracks.

Menoceras

A small two-horned rhinoceros that moved in herds. Agate holds some of the most complete Menoceras skeletons known, which is why it anchors the site’s fossil story.

Moropus

A tall, horse-like browser with claws instead of hooves. It used those claws to pull down branches and leaves, an odd build for a plant-eater.

Daeodon

An entelodont long known by the name Dinohyus, the “terrible pig.” It was a bone-crushing giant that scavenged carcasses, and it was far larger and stranger than any hog alive today.

Stenomylus

A small, slender, gazelle-like camel that grazed the open ground in herds. Its own quarry at Agate turned up rows of these delicate animals together.

The devil’s corkscrews

Some of the strangest fossils at Agate are not bones at all. Early researchers found tall spirals of hard rock twisting down into the ground, taller than a person, and had no idea what they were. The nickname stuck: devil’s corkscrews, or in the scientific literature, Daemonelix.

It took years of argument to settle the answer. The corkscrews are fossilized burrows, dug by Palaeocastor, a small land-dwelling beaver that lived in colonies on the dry Miocene plains rather than in the water. The animal spiraled down into the soil and lived at the bottom, and when the burrows filled and hardened they kept the shape exactly. The 1-mile Daemonelix Trail passes several of them preserved right where they were dug, roughly 20 million years ago.

How the fossils were found

The scientific story of Agate begins with a rancher. In the late 1800s, James Cook owned the land here, the Agate Springs Ranch a few miles from the fossil hills. Cook noticed unusual bones weathering out of the two hills and, rather than ignore them, invited scientists to look.

Among the first was Erwin Barbour of the University of Nebraska, who described the strange Daemonelix corkscrews. Paleontologists from major museums followed, and the digs of the early 1900s pulled complete skeletons out of the hills that reshaped what science understood about Miocene North America. Work at the site has never fully stopped, and researchers still return to its layers today.

Walk the fossil hills

The 2.8-mile Fossil Hills Trail crosses the ground where the great quarries were dug, with wide views over the Niobrara valley. The 1-mile Daemonelix Trail visits the corkscrew burrows. Fossil Hills starts at the visitor center; Daemonelix starts at the park’s west entrance.

See the monument guide

The Cook Collection: a Lakota legacy

The fossils are only half of what the monument holds. In the late 1800s and early 1900s, the Cook family’s Agate Springs Ranch became a gathering place, and James Cook formed a lasting friendship with Chief Red Cloud and other Oglala Lakota leaders who visited over the years. Out of that relationship came a collection of gifts, now cared for and displayed by the National Park Service at the visitor center.

The objects are personal and significant. Among them are a shirt and moccasins associated with Red Cloud, a large pipe tied to the Fort Laramie treaty negotiations, and a war club attributed to American Horse, along with beadwork and clothing. Together they record a friendship between a ranching family and Lakota leaders during a hard and painful period in the region’s history.

These belong to the Lakota story, and the meaning of the objects is the Lakota people’s to tell. We point visitors to the collection and to the interpretation at the monument rather than speak for it here.

What a visit takes in

Agate is quiet and uncrowded, well off the main tourist routes, and that is part of what makes it worth the trip. Here is what a day at the monument usually includes.

Two trails

The 2.8-mile Fossil Hills Trail and the 1-mile Daemonelix Trail, both easy walking on the open prairie.

Visitor center

Fossil skeletons on display, including Menoceras and Daeodon, plus the Cook Collection of Lakota objects.

Prairie wildlife

Pronghorn, mule deer, and burrowing owls live here, and meadowlarks sing across the grass in summer.

Dark skies

Little light for many miles means a deep, clear night sky, one of the best reasons to stay past sunset.

Free to visit

The monument charges no entrance or use fees. The visitor center has restrooms and water.

Getting there

34 miles north of Scottsbluff on Nebraska Highway 29, with the town of Harrison to the north.

Make a day of the Nebraska panhandle

Agate pairs naturally with Scotts Bluff National Monument, its sister park just to the south. The two share a superintendent and a stretch of the same panhandle country, and you can reach both in one day. Scotts Bluff was a landmark on the Oregon and Mormon trails, and its summit road and trails look out over the North Platte valley.

Plan the whole panhandle day

Our Scotts Bluff planning guide has drive times, trail options, and the summit road, so you can put Agate and Scotts Bluff together into one trip.

Plan a panhandle day
Explore Agate Fossil Beds

Keep exploring the monument

The complete guide

The full overview of Agate Fossil Beds National Monument, from fossils to Lakota history to planning a visit.

Artists in residence

How the artist-in-residence program connects art and nature at Agate Fossil Beds and Jewel Cave.

Scotts Bluff

Agate’s sister monument to the south, a landmark on the Oregon and Mormon trails.

Plan a panhandle day

Drive times, trails, and the summit road for pairing Agate with Scotts Bluff.

The Agate park store

Books, gifts, and field guides from the Agate Fossil Beds bookstore. Every purchase supports the monument.

Common questions about Agate Fossil Beds

Where is Agate Fossil Beds National Monument?
It sits in the far western panhandle of Nebraska, along the Niobrara River, about 34 miles north of Scottsbluff on Nebraska Highway 29. The small town of Harrison lies to the north. The monument is well off the main tourist routes, which keeps it quiet even in summer.
How old are the fossils?
The main fossil beds date to the early Miocene epoch, roughly 20 million years ago. The animals preserved here lived in a warmer, wetter country than today’s prairie, a time when grasses were still spreading across the plains.
What animals are found at Agate?
The best known are Menoceras, a small two-horned rhinoceros; Moropus, a clawed browser; Daeodon, the bone-crushing entelodont long called the “terrible pig”; and Stenomylus, a small gazelle-like camel. The site also preserves Daemonelix, the corkscrew burrows of the land beaver Palaeocastor.
What are the devil’s corkscrews?
They are tall, spiral fossils that puzzled early scientists, who nicknamed them devil’s corkscrews. In fact they are fossilized burrows dug by Palaeocastor, a small land-dwelling beaver of the Miocene. Several are preserved along the 1-mile Daemonelix Trail, right where they were formed.
What is the Cook Collection?
It is a collection of Lakota objects that came to the Cook family through James Cook’s friendship with Chief Red Cloud and other Oglala Lakota leaders who visited the Agate Springs Ranch. The National Park Service cares for and displays the collection at the monument’s visitor center. The objects belong to the Lakota story, and the monument’s interpretation is the place to learn what they mean.
Is there a fee, and what trails are there?
The monument charges no entrance or use fees. The 2.8-mile Fossil Hills Trail starts at the visitor center and crosses the historic quarry ground. The 1-mile Daemonelix Trail starts at the park’s west entrance and visits the corkscrew burrows. Both cross open prairie; see the official trail descriptions for current guidance.

Help keep Agate’s stories told

Black Hills Parks and Forests Association is the nonprofit cooperating association at Agate Fossil Beds National Monument. Memberships and the park store fund the interpretation, education, and exhibits that keep the fossils and the Cook Collection open to visitors.

Agate Fossil Beds National Monument is managed by the National Park Service. We acknowledge that this country is part of the ancestral homeland of the Lakota and other Plains nations, whose ties to it continue today.