Agate Fossil Beds near Harrison is an internationally recognized fossil site. The landscape surrounding the fossil beds has been a site of change for millions of years. Agate has also been a home to people like James and Kate Cook; leaders of great nations like Red Cloud and American Horse. The weathering of sedimentary rock, bones becoming visible in cliffs, and the gifts presented to James Cook by the Lakota Sioux are all reflective of the strong natural and cultural relationships of the Agate landscape. The Monument preserves bones in one of the best preserved Miocene mammal sites in the world.