Fossil Beds

The bluff across the river was found by a rancher who knew what he was looking at. Elmer Cook saw bones weathering out of it in 1928 and showed them to Harold Stearns of the Geological Survey, who passed word to the Smithsonian. The layers belong to the Glenns Ferry Formation, laid down by ancient Lake Idaho some three to four million years ago and cut open by the Bonneville Flood 15,000 years ago. More than 200 species have come out of them, eight known nowhere else. The beds became a national monument on November 18, 1988.

What the plaque says

Fossil Beds Fossil bones of zebras, beaver, otter, pelicans and other water birds are found in sediments left from a 3,400,000 year old pond on the bluff across the river. Lava flows, pouring out over the plains on this side, met and dammed up sedimentary deposits washed in on the other side, making lakes and swamps. Here the river divides these two important geologic settings, formed at a time when the climate was wetter, and the plains were tree-dotted grasslands where zebra-like horses used to graze. 300 Text prepared by the Idaho Historical Society Marker made & installed by Idaho Transportation Department

Where it stands

Worth the stop nearby

• Hagerman Fossil Beds National Monument — 8.4 mi
  Idaho's state fossil is closer to a zebra than a horse, and nearly the whole herd is in a museum in Washington.
• Box Canyon Springs — 13 mi
  The eleventh-largest spring in the United States, pouring from the head of a dead-end canyon with water that sank into the lava far to the northeast.

More markers nearby

• Salmon Falls — 10 mi
• Thousand Springs — 10 mi
• Fishing Falls — 13 mi
• Payne's Ferry — 13 mi