Serpent Mound, Ohio: Inside the Archaeological Mystery

By: Jesslyn Shields  | 
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Some believe the Fort Ancient culture built Serpent Mound in Adams County, Ohio, around 900 years ago. This prehistoric effigy mound is nearly a quarter of a mile long and represents a giant snake, possibly holding an egg in its jaws. MPI/Getty Images

Imagine you're living in ancient times in what is now Ohio. One day you and your friends decide: Let's make a 1,376-foot-long (419-meter-long) snake sculpture on the edge of this meteorite crater over here!

If only we had a time machine to ask you what possessed you and your people to make such a thing. But that's why we have archaeologists.


Serpent Mound, Ohio, located in southwestern Ohio, is a giant earthen mound — the largest serpent effigy in the world. Learn more about this archaeological mystery.

Did the Fort Ancient Culture Build Ohio's Serpent Mound?

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Serpent Mound snakes along a plateau above the Serpent Mound crater, an ancient meteor crater. Wikimedia Commons (CC BY-SA 4.0)

Some believe the Fort Ancient peoples constructed Serpent Mound around 900 years ago, although others argue that the site is much older and that the Fort Ancients did not build it but refurbished it.

Although archaeologists have not found any human remains or artifacts in the sinuous, grassy hillock that is Serpent Mound, some graves and burial mounds stand nearby, probably built by the Adena culture — the Fort Ancient people's predecessors in the area — around 500 C.E.


Regardless, Serpent Mound belongs to a class of structures called effigy mounds, structures built in the shape of animals like bear, lynx, bison or birds that often served as burial sites for ancient people.

Serpent Mound as a Calendar

Serpent Mound sits on the edge of a meteorite impact crater, and the serpent itself is between 19 and 25 feet (6 and 7.5 meters) wide and rises around 3 feet (1 meter) from the surrounding landscape, with its head formed by a rock cliff overhanging a nearby creek.

Although it's difficult to know what its purpose was since it wasn't used for burials, it acts as a calendar — the sunset on the summer solstice lines up with the serpent's head.


The three eastern-facing curves of the snake's body line up with the sunrise on the equinoxes, and the serpent's tail coils align with the winter solstice.

Is Snake Mound on the World Heritage List?

According to Ohio History Connection, in 2008, the U.S. Department of the Interior chose Serpent Mound and eight other Ohio American Indian earthworks for inclusion on the United States' tentative list of sites to submit to UNESCO (the United Nations Educational, Scientific, and Cultural Organization) for inclusion on the prestigious World Heritage Sites list.

Other sites on that list include the pyramids of Egypt, the Great Wall of China, Pompeii, Stonehenge and the Taj Mahal.


While still on UNESCO's tentative list, the organization says that it is of outstanding universal value:

"[The] monumental geoglyph embodies fundamental cosmological principles of an Indigenous ancient American Indian culture. Serpent Mound represents the acme of prehistory effigy mound-building in the world and is part of a tradition of effigy mound building among American Indian cultures of the present Eastern United States. Its remarkably naturalistic quality makes it immediately recognizable as a representation of a serpent, and the form also aligns astronomically to mark the passage of the seasons. The Great Serpent was a source of enormous spiritual power that a widespread pre-Columbian culture could invoke to aid them in hunting and in curing illnesses."


How to Visit Serpent Mound State Memorial

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Serpent Mound is on Brush Creek in Adams County, Ohio. This map appeared in "Ancient Monuments of the Mississippi Valley" by E. G. Squier in 1848. NNehring/Getty Images

Serpent Mound, located within the Serpent Mound State Memorial, is a National Historic Landmark in Peebles, Ohio. Here, you'll find a Serpent Mound museum with exhibits that delve into the geology of the area.

The site does not open Mondays and on a few holidays but maintains visitor hours all other days of the week.