David Haddenham in one of his quarries on Fossil Butte

Fossil fishes have attracted scientists and commercial fossil collectors to Fossil Butte National Monument since its discovery in the late 1800s. David Haddenham quarried on Fossil Butte from the early 1900s until the early 1950s. Haddenham and Robert Lee Craig, a contemporary collector across the valley, sold specimens to fossil collectors and museums around the world. Largely through their efforts the fossils of ancient Fossil Lake became world renowned.

Today, on private and state-owned lands outside Fossil Butte National Monument, many commercial fossil collectors quarry the limestone rock deposited in the ancient lake. Primarily through their efforts we now know that the ancient ecosystems included 27 species of fish including the world's only articulated freshwater stingrays, eight species of primitive mammals including the world's oldest articulated bats, over 300 species of plants including palm fronds, ferns, Equisetum (scouring rush), a large variety of deciduous leaf species, two snake species, three lizard species, two crocodilian species, seven turtle species, over 25 bird species, shrimp, crayfish, ostracods, and numerous insects waiting formal identification or scientific description. These fossils make this the most abundant, diverse, and exceptionally preserved eocene (52 million years old) fossil deposit in the world.