Chapman reports that, in 1835, a pair of Ypsilantians were digging clay from the face of "the eastern plateau" to use as fill dirt when their shovels struck timbers. Their investigation revealed a small, buried room in the side of the plateau, approximately ten feet square and eight feet in height; the entrance was a tunnel 100 feet long that emerged in dense shrubbery "near Dr. Davis' present residence". The cave contained a small furnace, and was "doubtless the hiding place of a gang of counterfeiters, if not of more terrible enemies of human happiness."
Chapman's recounting locates the den approximately 20 rods (330 feet) south of Congress Street, a location that may place it somewhere between South Grove and South Prospect streets, assuming that "the eastern plateau" is the abrupt rise encountered on eastbound Michigan Avenue on its way up to Prospect. Chapman seems to believe the counterfeiter's den pre-dated the first permanent American settlers to the Ypsilanti, but cannot place a date on its construction.
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