Ohio's Serpent Mound Is an Archaeological Mystery

By: Jesslyn Shields  | 
serpent mound
Serpent Mound in Adams County, Ohio, is believed to have been built by the Fort Ancient people around 900 years ago. This protected historical earthwork 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 a person living in ancient times in what is now the state of Ohio. Your job is mostly to grow corn and hang out in your village, providing all the necessities of life for yourself and your community — making pottery to cook in, maintaining your home and working to procure food other than corn. But one day you're talking to some friends and you 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, our friend from ancient times, what possessed you and your people to make such a thing. But that's why we have archaeologists.


Located in southwestern Ohio, Serpent Mound is a giant earthen mound — the largest serpent effigy in the world — thought to have been constructed by the Fort Ancient people around 900 years ago, although some argue that the site is much older and that the Fort Ancients did not build it, but actually refurbished it. Although no human remains or artifacts have been found 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, which were commonly built in the shape of animals like bear, lynx, bison or birds, and often served as burial sites for ancient people.

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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)

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.

According to Ohio History Connection, Serpent Mound and eight other Ohio American Indian earthworks were chosen in 2008 by the U.S. Department of the Interior for inclusion on the United States’ tentative list of sites to be submitted to UNESCO (the United Nations Educational, Scientific, and Cultural Organization) for inclusion on the prestigious World Heritage Sites list. If it is eventually inscribed on the list — possibly in 2023, according to Ohio History Connection's World Heritage Director Jennifer Aultman — Serpent Mound will join the ranks of the pyramids of Egypt, the Great Wall of China, Pompeii, Stonehenge and the Taj Mahal as World Heritage Sites.

Serpent Mound is located within the Serpent Mound State Memorial, designated a National Historic Landmark in Peebles, Ohio. The site is closed Mondays, but maintains visitors hours all other days of the week.

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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