Agate Fossil Beds National Monument in northwest Nebraska was established a mere quarter century ago—in June 1997—but its famed mammal fossils date to the early Paleocene Epoch, just after the mass extinction of dinosaurs 65 million years ago. Dozens of fossil skeletons were discovered in this modest valley, fed by the Niobrara River, in the early 1900s, with some of the most impressive specimens—such as the giant pig Dinohyus and rhino-like Menoceras—displayed in the park visitor center. There is some limited hiking in the park—effectively two trails—and one climbs to the excavation sites at aptly-named Fossil Hills, a pair of high knobs overlooking the Niobrara valley. Although you should not expect to find any ancient skeletons on the hike, there are many interpretive signs—and expansive panoramic views—along the way.
Agate Fossil Beds National Monument spans an austere valley in northwest Nebraska, south of the coniferous Pine Ridge and north of the Platte River Valley. Commercial amenities are dozens of miles distant in either direction; the nearest locality—known as Agate—is merely a single ranch set in an irrigated basin, at the junction of Route 29 and River Road, just west of the park. The remoteness of the national monument is part of its appeal, though a relatively large Visitor Center offers restrooms, exhibits, and, of course, the fossilized skeletons of several early Cenozoic era mammals.
The Fossil Hills Trail, one of two official hikes, begins and ends just outside the Visitor Center. Look for a paved track heading eastward from the building, keeping the parking area and a picnic pavilion on the left and a pair of recreated teepees on the right. Come to the first trail wayside, which offers a map and information on the trail, with a second steps later on invasive plant species. Curiously, just beyond, the Fossil Hills Trail splits, but the two paved tracks come back together in a few dozen yards, forming an oval of sorts through the grassy plain.
Head east, approaching a set of wetlands below the elevated hillsides to the south. At about 2/10 mile, hikers embark on a boardwalk section that traverses the marshy floodplain of the Niobrara River; this waterway, far wider and mightier downstream, is barely more than trickle at this point, well upstream from the river’s mouth.
Once across the stream, the Fossil Hills Trail winds southward and begins a mild but steady ascent, climbing up into the prairielands above the Niobrara Valley. The sun-soaked path skirts a minor uplift on the right and comes to a small shelter and bench at ½ mile. Stop here on a hot day for a drink and a breather. Here one can also read about Lieutenant Governeur K. Warren, who explored the area in 1857.
Up to the right (southwest), hikers can see the partly-exposed escarpments of University Hill and Carnegie Hill, the two “Fossil Hills” where paleontologists unearthed the specimens of various mammal species. Hikers will soon be atop a ridge between these two hills. But first, a steady climb is in order, with the still-paved track passing a sign for the “Bone Cabin” on the right and reaching a second sun shelter at 0.95 miles.
It is a short walk from here to a right-hand bend, which leads into another ascent, this time a straight shot up to the high saddle between University and Carnegie Hills. Stay right at the fork to take a short spur to the edge of University Hill, where there is an exposed section of agate but no fossils. Interpretive waysides explain how the rock layers reveal evidence of an ancient watering hole, frequented by species, long extinct today, like the Dinohyus, or “terrible pig.”
Around the start of the 20th century, Professor Erwin Balbour of the University of Nebraska led the fossil excavation effort here at the University Quarry. Astute observers can locate where bones were removed from the striated wall on the right, but those expecting to see fossils are likely to be disappointed. Hikers can also look down at the Niobrara Valley and the ridge bearing “Quarry A,” site of a dig led by the Carnegie Museum’s Olaf Peterson in 1904.
From the end of the spur, turn around and head south at the junction, staying right (twice) and coming to a short connector before the start of a short, ¼-mile loop around Carnegie Hill. Heading clockwise, the trail continues south, climbing to another shade shelter and a high gap. Here there is a wayside on the “beardog,” a carnivorous, wolf-sized animal whose skeletal remains were found in dens along this ridgeline.
Once over the saddle, the trail bears westward, with nice views across the valley, and approaches the flank of Carnegie Hill. Here the exposed agate (wedged between layers of limestone and sandstone) is more extensive, with the walls rising to 20- to 30-feet high. Three more waysides offer additional details on the mammals found here, including the rhino relative Menoceras and tall omnivorous Chalicotheres. This hill was excavated between 1904 and 1923.
Finally, past the main bonebed, the trail rounds to the north side of the hill and completes the loop portion. Now 1.6 miles into the hike, it’s time to retrace your steps back to the Visitor Center, shedding about 150 feet in elevation over the course of 1.2 miles. Passing patches of sunflowers and the initial wetlands, the Fossil Hills Trail ends back at the Visitor Center and parking area, finishing at 2.8 miles in total.