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.
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.