High Quality Content by WIKIPEDIA articles! Gardiners Island, a small island in the town of East Hampton, New York, in eastern Suffolk County; it is located in Gardiners Bay between the two peninsulas at the eastern end of Long Island. It is 6 miles (10 km) long, 3 miles (5 km) wide and has 27 miles (43 km) of coastline. The island has been owned by the Gardiner family and their descendants for nearly 400 years, and it is the only American real estate still intact as part of an original royal grant from the English Crown. Although occasionally reported as the largest privately owned island in America or the world, it is not.