Established in 1989, the Stonerose Interpretive Center and Fossil Site is an Eocene Epoch fossil site and accompanying interpretive center, located in Republic, Washington, part of the Okanagan Highland. The fossils are from organisms that lived in the area nearly 50 million years ago when the area that is now the city of Republic was part of an ancient lake. The old lake's bottom layers are now volcanic ash hardened into sedimentary rock, becoming fine-grained tuffaceous shale.