Hart Island, sometimes referred to as Hart's Island, is located at the western end of Long Island Sound, in the northeastern Bronx in New York City. Measuring approximately 1 mile long by 0.33 miles wide, Hart Island is part of the Pelham Islands archipelago, to the east of City Island.
The island's first public use was as a training ground for the United States Colored Troops in 1864. Since then, Hart Island has been the location of a Union Civil War prison camp, a psychiatric institution, a tuberculosis sanatorium, a potter's field with mass burials, a homeless shelter, a boys' reformatory, a jail, and a drug rehabilitation center. Several other structures, such as an amusement park, were planned for Hart Island but not built.
Wikipedia https://en.wikipedia.org/wiki/Hart_Island_(Bronx)
Coordinates 40°51'14.164" N -73°46'11.716" E