The 450lb solid iron cannonball was examined by the NYPD bomb squad, the FDNY, and Mike Shaver, a National Park Service ranger on Governors Island and expert on 19th-century artillery. The ball was located just behind a seawall at the main ferry dock on Governors Island. The ball was likely stocked on the island during the Civil War and never shot, then used as construction material for the seawall in the early 1900s.