Fossil Butte National Monument
Exceptionally complete fossils preserve an entire warm Eocene lake community, from stingrays and bats to insects, palms, and tiny horses.
Artwork inspired by Hans Kleiber
Fifty-two million years ago, a freshwater lake spread across parts of present-day Wyoming, Utah, and Idaho. Fossil Butte protects only a small portion of that basin, but its Green River Formation fossils are unusually abundant, diverse, and articulated. Oxygen-poor, salty bottom water discouraged scavengers, while microbial mats held remains in place as fine sediments accumulated. That combination preserved fish, turtles, crocodilians, plants, insects, birds, the oldest complete bats, and complete freshwater stingrays with startling detail.
Begin inside the visitor center, because the fossils themselves are not visible along the trails. More than 2,000 specimens, a wall of original fossil fishes, touchable material, and the preparation laboratory turn flat slabs into a readable ecosystem. Then take the Historic Quarry Trail or scenic drive to see where the fossil-bearing layers sit in the ridge. The landform looks like an isolated butte from the road, but geologically it is part of a longer curved ridge.
Summer adds the most direct look at the research process. On scheduled quarry-program days, visitors can hike three-quarters of a mile and climb more than 300 feet to watch fossils emerge; anything found remains in the monument collection for study. Collecting any fossil or other natural object inside the monument is illegal. Nearby private and state-land quarries may offer paid digging, but those businesses are separate places with separate rules.
- Age
- About 52 million years
- Display
- 2,000+ fossils
- Trails
- 4 maintained miles
Quick guide
- First question
- Original fishes on the visitor-center Fish Wall
- Set beside it
- The oldest complete bat fossils ↔ Fossil layers along the Historic Quarry Trail
A focused visit to Fossil Butte National Monument
- Begin
- Reconstruct the Eocene lake from the visitor center’s 2,000-plus specimens.
- Look closer
- Compare articulated fish, wing venation, leaves, bats, and stingrays.
- Go outside
- Use the Historic Quarry Trail to locate fossil-bearing strata in the ridge.
- Know boundaries
- Nothing may be collected inside; fee-dig quarries are separate businesses.
Good to know
Fossils are displayed indoors, not exposed on the trails. The park has no camping, lodging, or food service; Kemmerer and Diamondville are about 12 miles away. The unpaved upper scenic drive is narrow and steep, so large RVs and vehicles towing trailers should turn around at the picnic area.
Notice these
- Original fishes on the visitor-center Fish Wall
- The oldest complete bat fossils
- Fossil layers along the Historic Quarry Trail