From the glacier-flattened northwest to the Appalachian hills and valleys to the east and south, barns dot the Ohio landscape. Built with wooden nails and mortise-and-tenon joints and assembled with beams hand-hewn from nearby trees, some of these magnificent structures have witnessed three centuries. Many display the unique carpentry of masterful barn builders, including mystery wooden spikes and tongue-and-groove two-inch flooring. Sadly, a number...