Thousands of years ago, Native American peoples populated the Ohioan landscape with mounds and massive earthworks. Initial research attributed the effigy to the Adena culture, which flourished from 1000 BC to 100 AD. The Adena culture are well-known for building burial and effigy mounds, many of which are located near the Great Serpent Mound. However, radiocarbon dating on pieces of charcoal found within the Serpent Mound established that people worked on the mound around 1070 AD. Thus, the mound may have been built by the Fort Ancient peoples, who lived in the Ohio Valley from 1000 CE to 1550 CE. Nevertheless, the testing is not conclusive as it only reveals that 1000-year-old charcoal was found within the mound. This could have ended up there long after the effigy was originally built.