From Ohio History Central
The Cowan Creek Mound was a conical burial mound located in Vernon Township, Clinton County, Ohio. Raymond Baby excavated the mound in the late 1940s. At the base of the mound, he uncovered a circular pattern of postmolds 45 feet in diameter. He found many small, thick fragments of charred bark around the postmolds and concluded that these features represented an ancient house that had been roofed with bark. This was the first discovery of a circular pattern of postmolds beneath a mound in Ohio.
A radiocarbon date for the site indicated it was built at around 440 BC, placing it in the Adena culture.