Governors Island is a island in New York Harbor, within the New York City borough of Manhattan. It is located approximately south of Manhattan Island, and is separated from Brooklyn to the east by the Buttermilk Channel. The National Park Service administers a small portion of the north of the island as the Governors Island National Monument, including two former military fortifications named Fort Jay and Castle Williams. The Trust for Governors Island operates the remaining , including 52 historic buildings, as a public park. About of the land area is fill, added in the early 1900s to the south of the original island.