"There being one of these [mounds] in my neighborhood, I wished to satisfy myself whether any, and which of these opinions [regarding the identity of the Mound Builders] were just. For this purpose I determined to open and examine it thoroughly." (Thomas Jefferson)

In the 18th century, when Europeans first came upon the giant mounds and earthworks dotting the North American landscape, they couldn't imagine that the Native Americans they came into contact with were capable of producing such advanced technology and masterful engineering. In fact, when President George Washington sent adventurer and military strategist Rufus Putnam to survey the land at the convergence of the Ohio and Muskingum Rivers in southeastern Ohio for settlement, Putnam reported that he'd discovered an impressive walled earthwork complex near present-day Marietta, which was obviously the breastwork of an ancient fortress built by some long-forgotten ancient civilization. Like others of his time, Putnam couldn't conceive that indigenous Americans had at one time reached an advanced level of cultural and technical sophistication.

As detailed by Thomas Jefferson in his 1783 book Notes on the State of Virginia, the future American president began to excavate a mound near Monticello, his Virginia estate, around 1780. He noted, "I determined to open and examine it thoroughly. It was situated on the low grounds of the Rivanna [River], about two miles above its principal fork, and opposite to some hills, on which had been an Indian town. It was of a spheroidical form, of about 40 feet diameter at the base."