Coast Guard. When the Governors Island Coast Guard base closed in 1997, the Coast Guard's Civil Engineering Unit Providence stabilized the building with temporary replacement windows, repointing, stone patching with Jahn Mortar and a new roof. In 2003, Castle Williams and the neighboring fortification, Fort Jay, were transferred to the National Park Service under the administration of the Governors Island National Monument. It is listed on the National Register of Historic Places. See also List of New York City Designated Landmarks in Manhattan on Islands National Register of Historic Places listings in Manhattan on islands References Notes Bibliography "Castle Williams" on Historic American Buildings Survey (HABS) External links Explore Castle Williams - National Park Service Military facilities on the National Register of Historic Places in Manhattan Castles in the United States Forts in Manhattan American Civil War prison camps New York City Designated Landmarks in Manhattan Defunct prisons in New York (state) War of 1812 forts Infrastructure completed in 1811 1807 establishments in New York (state) Governors Island Museums in Manhattan Military and war museums in New York (state) Forts on the National Register of Historic Places in New York (state) American Civil War on the National Register of Historic Places