Who Built Serpent Mound and Why?

October 19, 2018

Serpent Mound

Serpent Mound in Adams County is one of the most interesting prehistoric sites in America. While ancient earthen structures of all types dot the Midwest, this effigy mound, on a narrow plateau overlooking Brush Creek, is the largest of its kind measuring in at 1,348 feet. While it’s length is impressive, it’s surprisingly short, rising only about 3 feet above the surrounding terrain. As the name suggests, it is in the shape of a giant serpent which at the head end appears to be poised to ingest an egg.

It may have been seen discovered by Euro-Americans around 1815. It wasn’t until 1848, though, that Ephraim Squire and Edwin Davis studied it and published their findings in a book titled Ancient Monuments of the Mississippi Valley, published by the Smithsonian Museum.

In 1900, the Herbert Peabody Museum, who had purchased the land years earlier, gifted the 53-acre site to the Ohio Historical and Archaeological Society who turned it into a public park. Today it is owned by the Ohio Historical Connection and has been managed by the Arc of Appalachia since 2009. The mound also sits in Ohio’s only exposed meteor crater, formed when a meteorite struck the area between 248 and 286 million years ago.

Who exactly built the Serpent Mound, and its precise purpose, is still a subject for debate. Unlike many mounds found in the Midwest, it’s not a burial mound. Various excavations since the mid-19th century have produced no artifacts according to Randy Mickle, education coordinator for Serpent Mound Site.

It was constructed by either the Adena or Ft. Ancient cultures, the latter being the most likely builders; depending on who you ask. What makes the determination difficult is the fact that both cultures lived in the area, the Adena from 1000 to 200 BC, followed by the Ft. Ancient culture arriving 1200 years later in 1000 CE and disappearing, somewhat mysteriously, around 1650, just before the arrival of Europeans. In between the Adena and Ft. Ancient cultures, the Hopewell tradition flourished, but there is no sign they took up permanent residence near Serpent Mound.

Carbon dating on charcoal fragments from the mound indicates it may have been built around 1050 CE placing it within the Ft. Ancient culture’s time in the area. However, other studies place its construction date to be between 300 and 40 BC meaning it was the Adena. The newer charcoal samples could have been from repair work conducted by the Ft. Ancient culture. In either case, since no artifacts were found, the mound clearly was not a burial structure.

“At sunset on the summer solstice,” Mickle explains, “the sun lines up about a degree off the head. You have to figure after a thousand years the Earth has moved a little and the alignment is not perfect. It was probably a ceremonial mound. The Fort Ancient people had a great reverence for the Sun and the Moon.”

The effigy also bears a striking resemblance to the constellation Draco which is home to the star Thuban, or Alpha Draconis, which in ancient times would have been the North Star.

Both the Adena and Ft. Ancient peoples lived immediately south of the mound in the area that today sits between the effigy and the parking lot. While this had been known for quite some time, it was only within the last six years or so that some interesting details began to emerge. “They used ground-penetrating radar,” Mickle says, “and a magnetometer to study everything, and it turns out the village was much larger than they thought. They found an Adena village and then a Fort Ancient village on top of that.” Two burial mounds are also on the site, two from the Adena Culture and one from Ft. Ancient.


A burial mound and side view of Serpent Mound.

The park is open daily, dawn til dusk and features an observation tower from which you can get a birds-eye view o the mound and surrounding countryside. The museum, featuring artifacts, recreations, and video presentations, is open daily from April through October and weekends in March, November, and part of December. Visitors can also view maps and aerial photos of other area mounds including those in Newtown, as well as the outline of a giant structure in Milford between Lila Avenue and the athletic fields north of the Little Miami (below).

Aerial imagery shows an effigy structure in Milford.


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