Fossil Butte National Monument
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 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. Scientists know all of this because these ancient flora and fauna became some of the most remarkably well-preserved and detailed fossils ever found. Over the last 100 years paleontologists and private collectors have unearthed millions of fossilized specimens. Many billions more remain buried.

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.