The Old Stone Fort is a prehistoric Native American structure located in Coffee County, Tennessee, in the Southeastern United States. The structure was most likely built between 80 and 550 AD during the Middle Woodland period. It is the most complex hilltop enclosure found in the South and was likely used for ceremonial purposes rather than defense. The structure is now part of Old Stone Fort State Archaeological Park, one of two archaeological parks in Tennessee (the other being at Pinson Mounds near Jackson). The site is listed on the National Register of Historic Places. Geographic setting The Old Stone Fort is located on a peninsula created by the confluence of the Duck River and the Little Duck River (the section of the Duck River upstream from its confluence with the Little Duck is sometimes called "Barren Fork"). The Duck River forms the peninsula's northwestern boundary, the Little Duck forms the peninsula's southeastern boundary, and a westward bend in the Little Duck forms the peninsula's southern boundary. The walled area of the structure encompasses approximately . (Click for Map) The Duck River system spills over a limestone-rich shelf of the western Cumberland Plateau known as the Highland Rim. As the Duck and Little Duck approach their convergence, they rapidly drop in elevation, and have cut relatively deep gorges around the peninsula upon which the ancient structure is located. Both gorges are highlighted by a series of substantial waterfalls and whitewater rapids. The natural waterpower in these two gorges attracted entrepreneurs and millwrights throughout the 19th century. The Old Stone Fort is located entirely within Coffee County, and is situated just west of Manchester, Tennessee. Old Stone Fort State Archaeological Park encompasses and is managed by the Tennessee Department of Environment and Conservation. The structure of the Old Stone Fort The walls of the Old Stone Fort consist of stone and earthwork, and are on average approximately 4–6 feet high. The walls originally consisted of an inner and outer layer of crudely stacked rocks and slabs with gravel and earthen fill in between. Over the centuries, the earthen fill has spilled over the rock layers, giving the walls their current mound-like appearance. The walls can be divided into roughly three sections, with two sections running roughly parallel to the Duck and Little Duck Rivers, and a third section running parallel to the southern rim of the peninsula. The sections paralleling the