Originally the Agate Springs Ranch, a working cattle ranch owned by Capt. James Cook, the site is best known, however, for the large number of well-preserved fossils which have been discovered, particularly at dig sites on Carnegie and University Hills. Fossils from the site are among some of the best specimens of Miocenemammals, such as Miohippus, an ancestor of the modern horse, and Menoceras, a three-toed, pony-sized rhinoceros. The monument's museum collection also contains more than 500 artifacts from the Cook Collection of Plains Indian artifacts.
