One Sunday afternoon in October of 1869, Stubb Newell, a farmer in upstate New York, invited his neighbors over to view the remarkable discovery he made while digging a well on his Cardiff farm. When they arrived, he showed them the body of a ten-foot-tall “petrified” man, lying at the bottom of a shallow pit where Newell had instructed workmen to dig.

The giant was a magnificent sight: A stone man naked in repose, seemingly at peace. It could hardly have …