The cultural horizon at the Sister’s Hill Site has produced typical Hell Gap points and a small group of associated artifacts. The radiocarbon date of 9650 ± 250 B. C. is in agreement with late Agate Basin or early post Agate Basin sites in the High Plains. On the basis of the current data, Hell Gap points appear to have developed from Agate Basin styles and seem to be developmental to Alberta, Scottsbluff and Eden types.