Miller Cave-Fort Leonard Wood in Missouri. This cave contains archaeological evidence of human occupancy from 7,000 B.C. to A.D. 1,400. Artifacts from this cave are displayed in the Smithsonian Institution, in Washington D.C. Miller Cave is part of a cave complex in the bluffs above the Big Piney River, along the southern boundary of Ft. Leonard Wood. One of the largest caves on Fort Leonard Wood, it is the only one open to the public.