Serpent Mound

The largest effigy mound in the world is also one of the hardest to date, and one of the most fought-over in the present.

The dating problem. It has no burials and no artefacts of its own, so it cannot be dated from its contents. Nineteenth-century investigators tied it to the Adena culture of around two thousand years ago, on the strength of nearby burial mounds. Radiocarbon work in the 1990s, on charcoal from the body of the mound, pointed instead to about 1070 and the later Fort Ancient culture. More recent excavation has reopened the older date, and proposed that the mound was built in stages. The honest statement is that its age is unsettled and the argument continues.

The alignments. The one thing most investigators agree on is that it is oriented: the open jaws and the oval align with the summer-solstice sunset, and the coils have been argued to track other solar and lunar events. What the serpent meant to its builders (a specific being, a calendar, a boundary), is inference.

The contest now. Serpent Mound has become a magnet for New Age and neo-pagan gatherings, drawn by ideas about earth energies that have nothing to do with the people who built it, and these proceed without the sanction of the Shawnee and other descendant nations who hold ties to the Ohio-valley mound builders. When the Ohio Hopewell Ceremonial Earthworks were inscribed as World Heritage in 2023, Serpent Mound was deliberately left out, because it postdates the Hopewell; it is now being advanced for a listing of its own.

Serpent Mound's coiled form is not just a shape; part of it lines up with a specific point on the horizon that only happens once a year.

An alignment built into the curves

The mound's head and the oval form near it are positioned such that the head aligns with the sunset position at the summer solstice, an alignment argued by some researchers as deliberate astronomical design rather than coincidence, though as with many such claims at effigy and earthwork sites, intentionality is inferred from geometry rather than confirmed by any accompanying written record.

An effigy, not a burial mound

Unlike many prehistoric North American mounds built primarily for burial, Serpent Mound contains no significant burials of its own, distinguishing it as an effigy mound, a large-scale earthen sculpture built in the shape of an animal, a form found at a number of other sites in the Ohio and upper Mississippi valleys but rarely at this scale or level of preservation.

As this entry's companion article covers

The unresolved debate over which culture actually built the mound, with radiocarbon evidence pointing variously toward the Fort Ancient culture or the earlier Adena culture, and what that uncertainty means for dating the site with confidence, is addressed directly in this entry's companion article rather than repeated here.