• Knightia eocaena mass mortality

    Fossil Butte

    National Monument Wyoming

Natural Features & Ecosystems

Fossil Lake was approximately 50 miles long and 20 miles wide. The light colored ridges, visible from Cundick Ridge, are what's left of the Fossil Lake deposits.

View from Cundick Ridge.

NPS photo

Fossil Butte National Monument offers a window into life in southwestern Wyoming 50-million years ago during the Eocene Epoch. Today's high-desert environment of the national monument is a stark contrast to the sub-tropical lake environment of the past.

Did You Know?

Diplomystus dentatus, NPS photo of Fossil Country Museum specimen

Railroad workers played a major role in the discovery of fossils from the Green River Formation.  In the late 1860's, Union Pacific workers uncovered the first major fossil fish beds (Lake Gosiute) near the town of Green River, Wyoming.