An Ancient Earthwork in Southern Ohio
Serpent Mound, one of North America’s most recognizable archaeological landmarks, stretches approximately 1,350 feet along a bluff in southern Ohio. Its earthen form resembles a snake with a coiled tail and open jaws appearing to close around a roughly 120-foot-long oval mound. The monument overlooks a tributary of the Ohio River, and its alignment creates a striking astronomical effect: visitors at the site during the summer solstice can watch the sun set over the serpent’s mouth.
The carefully maintained grass-covered earthwork is now surrounded by a paved walking path, but its original setting would have looked markedly different. When it was constructed, the mound would have dominated a landscape with relatively few visible signs of large-scale human activity, aside from nearby burial mounds and a village. The builders also placed it within a landscape shaped by an ancient geological event: Serpent Mound lies inside a roughly five-mile-wide eroded crater, or astrobleme, created by a meteor impact approximately 320 million years ago.
A Long-Standing Archaeological Debate
Despite its fame, archaeologists have not reached a definitive conclusion about when Serpent Mound was built or which Native American culture constructed it. The earthwork has traditionally been associated with both the Adena culture, which flourished in the region more than 2,000 years ago, and the later Fort Ancient culture. Dating evidence and interpretations of the site have continued to fuel debate, in part because the mound itself contains limited material that can provide a clear construction date.
Recent research described by Archaeology Magazine proposes that Serpent Mound may embody a Native American creation narrative, suggesting that its meaning extended beyond the physical representation of a snake. The available account does not identify the researchers or provide the full details of the interpretation, but it highlights a growing effort to understand the earthwork through Indigenous cultural traditions rather than relying solely on comparisons with monuments elsewhere in the world.
Early Misinterpretations and Preservation
By the late 18th century, trees and brush had concealed much of the serpent’s shape. Indigenous communities, including the Shawnee and other peoples whose ancestors created the region’s extensive earthworks, had been displaced from their homelands and suffered severe population losses. When archaeologists Ephraim Squier and Edwin H. Davis visited the site in 1846, local farmers reportedly believed it might have been a defensive structure.
Squier and Davis identified Serpent Mound as an extraordinary effigy earthwork and produced the first detailed plan of the site. They also examined the oval feature within the serpent’s jaws, where they found evidence of a burned stone platform that may have functioned as an altar. However, their interpretation reflected the assumptions of their era. In an 1848 report, they speculated—without supporting evidence—that the serpent imagery might be connected to ancient Egypt, India, or England.
Protecting the Site’s Legacy
The mound faced serious physical threats before it received legal protection. A tornado damaged it shortly before the Civil War, and farmers later plowed through portions of the tail. Much of the earthwork might have been destroyed, as happened to many Indigenous mounds during the period, without the intervention of Harvard archaeologist Frederic W. Putnam.
In the 1880s, Putnam helped secure funds to purchase, excavate, and restore Serpent Mound. He also played a role in persuading Ohio lawmakers to protect the site. Yet even Putnam advanced an unsupported theory, arguing in 1890 that the monument may have been built by Celtic travelers. That idea, like earlier claims linking the mound to distant civilizations, illustrates how 19th-century investigators often overlooked the capabilities and cultural histories of Indigenous societies. Today, the central question is increasingly framed around the Native American communities who built, used, and understood the earthwork—although its precise origins remain unresolved.
