Describe the mounds built by Caddoan cultures in Oklahoma. Why were these mounds built?

Mound Builders, in North American archaeology, name given to those people who built mounds in a large area from the Great Lakes to the Gulf of Mexico and from the Mississippi River to the Appalachian Mts. The greatest concentrations of mounds are found in the Mississippi and Ohio valleys. The term "Mound Builders" arose when the origin of the monuments was considered mysterious, most European Americans assuming that the Native Americans were too uncivilized for this accomplishment. In 1894, Cyrus Thompson of the Smithsonian Institution concluded that the Mound Builders were in fact the Native Americans. Clarence Moore, who excavated numerous mound sites in the South between 1892-1916, believed the southern Mound Builders were heavily influenced by the Mesoamerican civilizations, an idea now generally discounted. he various cultures collectively termed Mound Builders were inhabitants of North America who, during a 5,000-year period, constructed various styles of earthen mounds for religious and ceremonial, burial, and elite residential purposes.