Ancient Culture, between the years of 1041 CE and 1211 CE Given the results found through carbon dating, burials in the conical mound dated to the Early Woodland and Fort Ancient periods, suggestive of ritual reuse of the circum mound area and ash bed. Serpent Mound Museum In 1901, the Ohio Historical Society hired engineer, Clinton Cowan, to survey newly acquired lands. Cowan created a 56 by 72-inch (1,800 mm) map that depicted the outline of The Serpent Mound in relation to nearby landmarks, such as hills and rivers. Along with this, Cowan made specific geographical surveys of the area, discovering a unique astrobleme on which the mound is based. He found that the mound is at the convergence of three distinctly different soil types. Cowan's information, in conjunction with Putnam's archaeological discoveries, has been the basis for all modern investigations of The Serpent Mound. Furthermore, a digital GIS map of Ohio's Great Serpent Mound was created by Timothy A. Price and Nichole I. Stump in March 2002. In 1967, The Ohio Historical Society opened The Serpent Mound Museum, built very close to the site of the mound. A pathway was constructed around the base of the mound, guiding visitors through and around the site. The museum features exhibits that include explanations of the effigy's form, description of the constructing of the mound and the geographical history of the area. The museum also features an exhibit on the Adena culture, which they historically credited as the creators of the mound. Serpent Mound State Memorial is currently being operated on behalf of the Ohio Historical Society by the Arc of Appalachia Preserve System. It is a non-profit organization that specializes in the preservation and protection of native biodiversity and prehistoric aboriginal sites in southern Ohio. See also Cahokia Crooks Mound Glades culture Indian Mounds Park Mound Builders Nazca Lines Spiro Mounds Marree Man List of impact craters on Earth List of impact craters in North America References Further reading Fletcher, Robert V., Terry L. Cameron, Bradley T. Lepper, Dee Anne Wymer, and William Pickard, "Serpent Mound: A Fort Ancient Icon?", Midcontinental Journal of Archaeology, Vol 21, No. 1, Spring 1996, University of Iowa. Putnam, Frederic Ward, "The Serpent Mound of Ohio: Site Excavation and Park Reconstruction.", Century Magazine Vol 39: 871–888. Illustrations by William Jacob Baer. Squier, Ephraim G. and Edwin H. Davis, Ancient Monuments of the Mississippi Valley, Smithsonian Institution