The original hospital at Fort Jay (Columbus) on Governor's Island was constructed in 1840. It was square in plan with two stories and a basement. The basement housed the surgeon?s office, dispensary, kitchen, and mess. The first and second floors housed the hospital wards. The building was constructed of brick. After the Civil War, two wood-framed wards were added to the back of the brick structure and the original structure was transformed into administration space and examination rooms. The entire complex was transformed into the Post Headquarters after the second hospital was constructed in the 1880s. At some point after World War I, the two ward wings were demolished and the administration building was changed into officers? quarters. [Image from the Library of Congress]

The northern half of Governor's Island is a National Register historic district #85002435. It's also a National Historic Landmark. The National Park Service runs Castle Williams and Fort Jay as a National Monument. The rest of Governor's Island is administered by the Governors Island Preservation and Education Corporation. The island is required by law to have no housing (which is a shame - I think the Presidio model works very well).