The John Roy Site is located in the U.S. state of Illinois. It is in or near the Adams County village of Clayton and listed on the U.S. National Register of Historic Places. The site is an important prehistoric village from the Woodland period, associated with the Mississippian culture. It is one of the sites the Register classifies as "address restricted," although many such sites are open to the public as parks. It is the only Registered Historic Place in Clayton, though others are found throughout the county, mostly in Quincy, Illinois.