Fossil Butte National Monument
The limestone on top of this butte is the bottom of a lake. Say it out loud in the parking lot before anybody goes inside, because everything else here follows from it.
The lake is gone and has a name. Fossil Lake sat here in the Eocene, and the rock it left is part of the Green River Formation, which records lake, river and floodplain deposits across three states. The fossils are about 50 million years old. What earns them a national monument is not that they exist but how well they came out: soft tissue, skin, the fine bones of a fin. NPS notes that preservation this good has its own word, Lagerstätte, and that it is what lets scientists read a whole extinct ecosystem instead of a list of species. The list is long anyway. Palm trees, insects, paddlefish, stingrays, gar, pike, trout-perch, herring, turtles, snakes, lizards, crocodiles, parrots, bitterns, goatsuckers, oilbirds, and mammals.
Congress set the monument aside on October 23, 1972, under Public Law 92-537, to preserve, in the law’s own words, outstanding paleontological sites and related geological phenomena. It runs to 8,198 acres in Lincoln County, about 13 miles west of Kemmerer.
Do the timeline before you go in the building. Journey Through Time runs along the road up to the visitor center and around the porch, at a scale of nine inches to one million years. It opens with the formation of Earth about 4.54 billion years ago. It ends, in the Park Service’s phrasing, at present day, almost simultaneously with the appearance of recorded human history.
Read that scale back to a child and let them do the arithmetic. Nine inches is a million years, so the fifty million years since the lake dried runs to more than thirty feet of roadside. Everything anybody has ever written down lands in the last twentieth of an inch, on the porch, at the end of the walk.
There are two sign systems here and they are easy to run together. Along the Scenic Drive, ten wayside signs start at the park entrance sign and cover the geology and the landscape in front of you. The deep-time walk is the one on the entrance road.
Every fossil at this monument is inside the building. NPS says so plainly: you will not find any on the trails, and you should not go looking.
The published exhibit list is longer than the building looks from outside. A Fish Wall with 16 species and 49 fossils. A Turtle Wall, 6 species and 9 specimens. A Primitive Fish Case with 8 species. A Plant Wall carrying over 100 fossil leaves. A Bird Wall with 4 species. A Mammal and Reptile Display, 9 species and 11 fossils. Then cases for insects, plant structures, coprolites, invertebrates, arthropods, flowers, seeds, trace fossils, fry and fingerlings, predator and prey, and one called Catastrophe.
Two of the exhibits are in the restrooms. Coprolites are fossilized droppings, and the park collected nearly 10,000 of them and prepared more than 4,000 to find pieces that fit back together. The result is 733 matching sets, shown across the two restroom exhibits.
The Scenic Drive is 5.5 miles. It is paved for the first 2.5, as far as the Nature Trail parking lot. After that it turns to gravel and climbs a 17 percent grade for the remaining three miles to the top of a ridge, where the valley opens out below you. Seventeen percent on gravel is a real number, and if you are driving something long or heavy or borrowed, the lot at mile 2.5 is a fine place to decide you have arrived. That is where ours stopped. The Park Service says the drive is only accessible late spring through early fall, so for most of the year the question does not come up.
The drive also reaches several unmaintained hiking trails. Unmaintained means what it says.
Historic Quarry Trail is a 2.5-mile loop that gains almost 700 feet and starts at 6,675 feet above sea level. NPS rates it moderate to strenuous depending on how acclimated you are to the elevation, which is a polite way of saying the altitude will do more to you than the climb will. It crosses the Wasatch and Green River Formations, carries wayside exhibits on the geology and the paleontology, and takes a short side loop up to the old quarry, where several flights of stairs climb the rock.
There is a Nature Trail at the end of the pavement. NPS names it on the Scenic Drive page and does not publish its length or its climb, so we are not going to invent either.
Practical notes. The park is open sunrise to sunset. The visitor center keeps its own hours and they change with the season, so check those rather than the park’s. NPS says the monument is open to visitors year-round. The Scenic Drive is not.
To get in, travel 9 miles west of Kemmerer on U.S. Highway 30, watch for the highway sign near mile post 44, and turn onto Lincoln County Road 300. Chicken Creek Road, about a mile and a half further west, is the turn in to the visitor center. The mailing address is P.O. Box 592, Kemmerer, WY 83101, and the phone is 307-877-4455. We are not quoting a fee in either direction, because NPS routes that question to a fees page rather than answering it in the basic information, and a wrong number costs a family more than no number.
Kemmerer is thirteen miles east and worth the stop on the way out. J.C. Penney opened his first store there on April 14, 1902, and the J.C. Penney Historic District, which takes in the former Golden Rule Store on South Main and the house he lived in, is a National Historic Landmark. The store trading in town today has been at its current location since 1929, so what you are walking into is the chain’s hometown and not its original room.
Diamondville sits against Kemmerer to the south and was a coal town. Both places are also the address of the Natrium reactor now going up near the existing coal-fired plant, which the NRC permitted in March 2026. A valley mined for coal is being wired for something else. You can see both from the same road.