These fossil beds, found in 1928 on C.C. Coffee Ranch by geologists of Rio Bravo Oil Company, were cited at the time of discovery as one of the most prolific fossil fields of lower Pliocene age and are about 13,000,000 years old. Reports of the find brought specialists from several major institutions to the area. Fossil bones buried here included those of a prehistoric camel, a kind of antelope, horse, bone-crushing dog, mastodon, and wild pig. Further studies led scientists in 1941 to adopt “Hemphillian” as the name for the geologic age represented by these fossils.