Fossil Butte National Monument

Fifty-two million years ago the American West was warm and wet, and a chain of large lakes filled the basins here. The one recorded at Fossil Butte, known to geologists as Fossil Lake, was ringed by palms and lush forest, with crocodiles in the shallows and turtles on the banks.

When plants and animals died and sank, the still, layered bottom waters and the steady rain of fine limy mud buried them before they could rot or scatter. Season after season those layers stacked up, and over millions of years they hardened into the thin sheets of rock that today split apart to reveal what lived and died in the lake.

The most common fossils are fish, especially a small herring-like fish called Knightia, which is so abundant and so tied to this place that it is the Wyoming state fossil. Alongside it are perch-like Priscacara, gar, paddlefish, and even freshwater stingrays.

But the lake bed holds far more than fish. Fossil Butte has yielded some of the oldest known bats, early birds, palm leaves the size of a person, insects with the veins still in their wings, and small early horses. Because the preservation is so fine, scientists can read details of soft bodies and life histories that almost never survive elsewhere.

The monument's visitor center is the place to start, with walls of original fossils, murals of the ancient lake, and often a preparator at work freeing a specimen from its slab. It turns an abstract idea into something you can stand in front of and study.

From there, trails climb the butte itself. The Historic Quarry Trail leads to the site where commercial and scientific digging first revealed the beds, and the Fossil Lake Trail loops through aspen and meadow with wide views. It is a chance to walk the shore of a lake that dried up long before there were people to see it.

The world above the fossils is classic high Wyoming: sagebrush steppe and aspen pockets under big skies, home to pronghorn, mule deer, elk, moose in the wetter draws, and the occasional badger or coyote. Raptors hunt the open slopes and the meadows fill with wildflowers in early summer.

Summer is the easiest season, with the visitor center open and the trails clear. Spring and fall are quiet and beautiful but cool, and winter brings snow and a near-empty monument. However you come, the contrast is the whole point: a cool, dry, windswept butte that was once a warm and crowded lake.

The closest Boutel™ stays, so you can turn this stop into an overnight. Each is an independently owned, editorially selected place to stay.