Hart Island is New York's public cemetery for the poor and forgotten. It is popularly known as Potter's Field, after the biblical potter's field the Pharisees bought with Judas's 30 pieces of silver and used for the burial of foreigners.

It is a strip of land in Long Island Sound, north-east of Manhattan, where bodies are shipped in pine boxes and piled up in mass graves. Prisoners from nearby Riker's Island lug the bodies and leave them under a tarpaulin until there are enough to fill a grave - 100 (or 1,000 infants) to a pit.

It's quite an achievement to have added to the mythology of the 20th century's most mythicised city, but that's what artists Melinda Hunt and Joel Sternfeld have done through photographs, texts and installation work. The Hart Island Project, at Manchester's Cornerhouse, tells a mind-boggling story about what happens to those who go to New York and don't find success.

Hunt, a Canadian-born artist who lives in Brooklyn and specialises in public art, began documenting Hart Island seven years ago. She invited American landscape photographer Sternfeld to go with her. His photographs of storm-blasted trees and decaying guards' houses and of tiny white markers above chil dren's coffins, have the tight-lipped grief of a country-blues ballad.

Most New Yorkers don't know about Hart Island. It is not a tourist attraction like Ellis Island: you need special permission to visit. Yet it's been calculated that every family that has come to New York since the 19th century has someone buried there.

In the 19th century the island also housed a prison for confederate soldiers which, at the turn of this century, was turned into a boys' reformatory. Sternfeld photographs rotting seats from Ebbet's Field baseball stadium, donated to the reformatory baseball team, and a pile of platform shoes the boys made.

Today the dead on the island are predominantly black prisoners on remand or convicted of drugs offences. A photograph of mainly white guards posing while black prisoners stack coffins in a trench could have been taken during the slavery era. Hunt and Sternfeld have excavated the nightmare unconscious of Manhattan, the place where all the New York stories end.