Clarence Hungerforf Webb studied which Caddoan culture sire 15 miles from the Mississippi River?
Clarence Hungerford Webb:  A distinguished physician, his archaeological research included the study of Caddoan culture, and at a number of major sites such as Poverty Point, John Pearce , Gahagan, and Belcher Mound. Poverty Point:  It is 15.5 mi from the current Mississippi River, and situated on the edge of Maçon Ridge, near the village of Epps in West Carroll Parish in northeastern Louisiana.
i don't know