Agate Fossil Beds National Monument Located in Harrison, NE TRAVEL BASICS - CAMPING - LODGING ACTIVITIES - FACILITIES - FEES/PERMITS The Fossil Hills (NPS Photo) IN BRIEF Located on the Niobrara River in northwestern Nebraska, the Agate Fossil Beds and its surrounding prairie are preserved in a 3, 000 acre National Monument. Once part of Captain James H. Cook's Agate Springs Ranch, the nearby ...