Serpent Mound — Public Lands Institute

Silurian433-427 Mya

~433 to 427 Mya Silurian Peebles Dolomite with the underlying Lilley and Bisher Formations, bluish gray, thick to massive bedded, vuggy to cavernous, up to 120 feet thick and a cliff former; the plateau sits on the southwestern part of the Serpent Mound impact structure, a crater about 14 km (8.7 miles) across formed 252 to 330 Mya, in which the surrounding Paleozoic beds were uplifted, dropped, faulted, and folded. The site lies in unglaciated Ohio.

Epoch

Silurian (Peebles Dolomite); late Paleozoic impact structure

Native lands Glossary →

Adena culture (about 800 BCE to 1 CE), to whom Putnam assigned the conical burial mound beside the effigy and whom 2014 radiocarbon dates on soil cores, corroborated in 2019, credit with building the effigy around 300 BCE · Fort Ancient culture (about 1000 to 1650 CE), to whom a 1991 excavation dating the effigy to about 900 years old assigns it, and whose ash bed north of the conical mound dates to 1041 to 1211 CE; of the three burial mounds beside the effigy, the Ohio History Connection identifies two as Adena and one as Fort Ancient, and Putnam found no artifacts in the serpent itself, so the 1,348-foot effigy's builders remain disputed · Shawnee (Shawanwaki) · Myaamia (Miami); the plateau overlooks Ohio Brush Creek in Shawnee country on the north side of the Ohio valley; Shawnee, Miami, and allied nations ceded southern Ohio via the Treaty of Greene Ville, August 3 1795, and the last Ohio Shawnee communities at Wapakoneta and Hog Creek were removed west under the treaties of 1831.

Displacement & Tenure

Cession 11: Treaty of Greene Ville (1795). Adams County lies in the Virginia Military District, reserved by Virginia in its 1784 cession of the Northwest to pay Revolutionary War bounty warrants and patented by metes and bounds survey to veterans, warrant assignees, and speculators. In 1886 Frederic Ward Putnam of Harvard's Peabody Museum, with money raised among Boston women led by Alice C. Fletcher, bought 60 acres holding the effigy, three conical mounds, a village site, and a burial ground; Harvard granted the property in 1900 to the Ohio State Archaeological and Historical Society, now the Ohio History Connection, which owns it. The Arc of Appalachia managed the site from 2009 until the Ohio History Connection took operations back in March 2021.

Shadow History

Serpent Mound is preserved because it was bought to be excavated. Putnam spent three seasons from 1886 digging the effigy and the mounds around it before rebuilding them. In the conical mound southwest of the serpent he removed the principal burial, an adult man laid on a platform and partly cremated under thrown clay, with flint points, a hematite core, a celt, two grooved axes, and bone awls, along with nine later burials set into the mound; in the oblong mound to the south he removed four people from stone graves, and other graves on the plateau gave up dozens more objects, one alone holding 30 points. The remains and grave goods went to the Peabody Museum at Harvard. The serpent visitors walk today is Putnam's restoration: the 1974 National Historic Landmark documentation states that his excavations were read as supporting the snake-swallowing-an-egg interpretation and that the present restoration conforms to it. No Federal Register NAGPRA notice naming Serpent Mound has been published as of November 2026, and the site's owner, the Ohio History Connection, held more than 7,000 Native American ancestral remains as of December 2024.

Ecology

The effigy and plateau are held in mown grass with scattered groves of hardwoods on a flat hilltop 100 feet above Ohio Brush Creek, the bluff slopes falling away in second-growth forest on dolomite.

Hydrology

Ohio Brush Creek along the base of the east bluff, about 100 feet below the effigy, flowing south to the Ohio River; East Creek bounds the plateau on the north and northeast.

Acreage

GPS

39.0264° N, 83.4308° W

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