It's a genealogist's worst nightmare: 800,000+ burials and only one marked grave.
Most New Yorkers don’t even know it’s there. Hart Island, near the popular summer spot City Island, is one of the world’s largest cemeteries, and the U.S.’s largest potter’s field, where the indigent and unidentifiable have been buried en masse since just after the Civil War.
At one time the island also housed a prison, a boys’ workhouse, a Nike Ajax nuclear missile silo, and for four months in 1865, it was a prisoner of war camp used to house captured Confederate Troops, more than 250 of whom died and were buried here. The only grave with a marker is that of an unnamed baby who died in 1980, New York City’s first AIDS casualty, buried in isolation. [Link]