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In 1916 William H. Spencer of Spencer, Wyoming found a number of well-worked prehistoric stone blades, and blade fragments eroding from a bank close to a spring in Moss Agate Arroyo. About 1931 he picked up another specimen not far from his original find. But it was not until the summer of 1941 that Spencer reported his finds to Robert E. Frison, who was at that time deputy game and fish warden at Newcastle. The following April Frison visited the site and subsequently wrote to Dr. Frank H. H. Roberts of the Bureau of American Ethnology, Smithsonian Institution, concerning the prehistoric site. In 1942 Roberts tested the area where the artifacts had been found and where bones were eroding from the bank. Not until the fall of 1958 was the site again brought to the attention of archaeologists. Excavations by a team from the University of Wyoming began in 1959. Multiple occupation levels were reported, including Agate Basin and Folsom. The site was a bison kill and procurement location dating to Paleoindian times. A long-term investigation of the site began in the mid 1970s under the direction of Dr. George C. Frison.