 agate fossil beds national monument is a u.s. national monument near harrison, nebraska. the main features of the monument are a valley of the niobrara river and the fossils found on carnegie hill and university hill. the area largely consists of grass-covered plains. plants on the site include prairie sandreed, blue grama, little bluestem and needle and thread grass, and the wildflowers lupin, spiderwort, western wallflower and sunflowers. ==history== the site is best known for the large number of well-preserved miocene fossils, many of which were found at dig sites on carnegie and university hills. fossils from the site, which date from about 20 million years ago, are among some of the best specimens of miocene mammals. species found at agate include: *miohippus, an ancestor of the modern horse, *menoceras, a pony-sized rhinoceros, *amphicyon, a bear dog, *daeodon, the largest entelodont (giant pig-like ungulate), *stenomylus, a gazelle-like camelid, and *palaeocastor, land beavers that dug large corkscrew-shaped burrows (daemonelix) originally the agate springs ranch, a working cattle ranch, was owned by capt. james cook. the monument's museum collection also contains more than 500 artifacts from the cook collection of plains indian artifacts. the national monument was authorized on june 5, 1965, but was not established until june 14, 1997. the harold j. cook homestead (bone cabin complex) was listed on the national register of historic places in 1977. agate fossil beds is maintained by the national park service.{{cite web |title=agate fos
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