~453 to 444 Mya Late Ordovician Waynesville and Arnheim Formations, interbedded gray to bluish gray shale and limestone 140 to 220 feet thick, capped on the plateau by glacial till; the Little Miami has cut 270 feet below the rim, and the builders used the local surface limestone for the stone-capped mounds and pavements.
Epoch
Late Ordovician (Cincinnatian Series, Richmondian)
Ohio Hopewell culture, who raised 3.5 miles of wall enclosing about 100 acres on the plateau between roughly 100 BCE and 400 CE · Fort Ancient culture (about 1000 to 1650 CE), whose Anderson village stood on the terrace inside the enclosure and which takes its archaeological name from this earthwork rather than the reverse · Shawnee (Shawanwaki) · Myaamia (Miami); the Little Miami a Shawnee travel corridor running up to Chalahgawtha (Old Chillicothe) north of present Xenia, the largest Shawnee town in Ohio from 1777 to 1780, burned by George Rogers Clark's 970 Kentucky militia in August 1780; Shawnee and Miami ceded southwestern Ohio via the Treaty of Greene Ville, August 3 1795.
Displacement & Tenure
Cession 11: Treaty of Greene Ville (1795). The earthwork lies east of the Little Miami in the Virginia Military District, the tract Virginia reserved in its 1784 cession of the Northwest to satisfy Revolutionary War bounty warrants and the only part of Ohio surveyed by metes and bounds rather than the rectangular township grid; the land passed to veterans, warrant assignees, and speculators. The State of Ohio bought the site in 1891 after Warren K. Moorehead lobbied the legislature, making it Ohio's first state park; the Ohio History Connection owns it and the Dayton Society of Natural History operates it.
Shadow History
Fort Ancient's archaeological record was largely removed before the site was protected. Moorehead surveyed and dug the enclosure's mounds and stone graves in the late 1880s and published the results in 1890 as Fort Ancient: The Great Prehistoric Earthwork of Warren County, Ohio, subtitled an account of its mounds and graves; Frederic Ward Putnam then hired him in 1891 to excavate Ohio Hopewell sites and collect human remains and objects for display at the 1893 World's Columbian Exposition in Chicago. Inside the present park boundary, the landowner Clifford C. Anderson dug the Fort Ancient culture Anderson village from 1893 to 1936, opening refuse pits, house patterns, and burials and recovering thousands of objects; material excavated with Robert A. Kercher between 1932 and 1936 was bought by a private collector in 1950 and given to the Smithsonian's National Museum of the American Indian in 1952. The Ohio History Connection, which owns Fort Ancient, held more than 7,000 Native American ancestral remains as of December 2024 and had completed 17 repatriations in the 34 years since NAGPRA passed in 1990, under one percent of its holdings; it is consulting with 45 nations tied to the Ohio Valley on an intertribal reburial ground. State Route 350 still runs through the earthwork's North Gate between the Twin Mounds.
Ecology
Second-growth oak and hickory with sugar maple, American beech, and tulip poplar on the north-facing gorge slopes above the Little Miami; restored prairie plots on the plateau inside the earthwork; more than 3.5 miles of trails through the ravine heads the walls enclose.
Hydrology
Little Miami River, 270 feet below the plateau rim; Ohio's first state scenic river, first section designated April 23 1969, and a National Wild and Scenic River from Clifton to Foster designated August 1973, this reach inside that segment; the enclosure walls follow the heads of steep unnamed ravines draining directly to the river.
