Discover Fossil Butte National Monument

Knightia eocaena is the world's most abundant articulated vertebrate fossil.  It is also Wyoming's state fossil.
Fossil Butte interpretive sign
Fossil Butte visitors

You wouldn’t know from looking at it today, but Fossil Butte National Monument used to be Fossil Lake. Back in the day — and by that we mean roughly 50 million years ago — you couldn’t have missed Fossil Lake if you tried. Fifty miles long and 20 miles wide, it was one of the Great Lakes of its time and was home to everything from dog-sized horses to stingrays and crocodiles. There were also 23 species of fish in the lake, and its banks were lined with palms and a wide variety of deciduous trees. These ancient flora and fauna became some of the most remarkably well-preserved and detailed fossils ever found and draw thousands of visitors every year to Fossil Butte National Monument.

No one knows for sure why so much of the life in Fossil Lake became a fossil, but the monument’s visitor center has a few ideas. After a peek inside the center and at its display of museum-quality fossils, hit one of two short interpretative hiking trails.

While you are not allowed to remove any fossils from the monument, there are nearby for-fee fossil quarries — the national monument doesn’t cover the entirety of the former lakebed. Everyone leaves the quarries with something.

Learn more about Wyoming's other fascinating archaeological and paleontological sites, and check out our weekend road trip itinerary through Southwest Wyoming.

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