Hart Island is in the Pelham Islands group, officially a part of the Bronx. East of the lively City Island, it is a grave site, New York City’s own potter’s field — a term from the New Testament that has come to denote a burial place for the poor, the anonymous, people without family or without family that can afford a marked resting place. The site is managed by the city’s Department of Correction and is not open to the public.

Brendan J. Byrne’s documentary “One Million American Dreams” guides the viewer through several true narratives of how one might end up there. These stories can be heartbreaking. There’s a mother who had no funds to bury her dead infant. And a Cuban émigré working to send money to his family back home, who fell prey to dementia before dying incommunicado.

Hart Island, the writer Luc Sante says in an interview, is emblematic of an indifference that all cities cultivate out of practical necessity. But in New York, he notes, the indifference is exaggerated.

A case in point: the story of one drug addict whose family was never contacted after his body was found, kept as a medical-research cadaver for three years before being shipped to Hart Island. It took a New York Times reporter little more than a single phone call to locate the man’s widow.