Spiro Mounds - Spiro Mounds is an important Pre-Columbian Caddoan Mississippian culture archaeological site located in present-day eastern Oklahoma. The site is located seven miles north of Spiro, and is the only prehistoric archaeological site in Oklahoma open to the public. The prehistoric Spiro people thrived and created a strong religious center and political system. The site was eventually abandoned after several hundred years of occupation, although it is still unclear why. The Great Mortuary at the site was looted in the 1930s. Many of the looted artifacts were eventually tracked down, although many others were destroyed by the looters, who used dynamite on the mound to gain access to its contents. The mounds site has been significant to North American archaeology since the 1930s, especially in the defining of the Southeastern Ceremonial Complex. Listed on the National Register of Historic Places, the site is under the protection of the Oklahoma Historical Society and open to the public.