[5] In 1938, plans were drawn up to build a facility for children who had an intellectual disability on 375 acres (152 ha) in the Willowbrook section of Staten Island.

"[8] Historian David Rothman notes that, "The research was even included in Henry Beecher's 1966 New England Journal of Medicine listing of 'ethically dubious' experiments.

US Senator Robert F. Kennedy toured the institution in 1965 and proclaimed that individuals in the overcrowded facility were "living in filth and dirt, their clothing in rags, in rooms less comfortable and cheerful than the cages in which we put animals in a zoo" and offered a series of recommendations for improving conditions.

Stone, an advocate for mentally disabled children and victims of child abuse, gained access to the school by posing as a recent social work graduate.

As a result of the overcrowding and inhumane conditions, a class-action lawsuit was filed against the State of New York by the parents of 5,000 residents of Willowbrook in federal court on March 17, 1972.

The publicity generated by the case was a major contributing factor to the passage of a federal law — the Civil Rights of Institutionalized Persons Act of 1980.

According to a February 2020 New York Times investigation "[t]hat vow has been broken: Many of the institution's 2,300 alumni who are alive today still suffer from mistreatment."

Investigations were conducted by the New York State Office for People With Developmental Disabilities but were unable to prove abuse claiming that "Strong union protections allowed them to block their dismissals in arbitration."

Bronx County District Attorney Darcel Clark investigated one facility that houses Willowbrook alumni but found insufficient evidence for abuse, witnesses not willing to come forward, and victims not able to speak for themselves.

Within the year, one of CSI's two other existing campuses, located in the Sunnyside neighborhood, was closed, renovated, and reopened in 1995 as the home of the new K-12 Michael J. Petrides School.

Some had cerebral palsy, a developmental disability that can be accompanied by varying degrees of intellectual impairment, and some members of this class were cognitively quite intact, yet unable to communicate verbally due to their physical condition.

These ex-residents of Willowbrook, many now in their 50s and 60s, live in a variety of community residences and attend day programs throughout New York State, under the care of organizations such as United Cerebral Palsy or the Jewish Guild for the Blind.

"[17] Writes The New York Times reviewer, Stephen Holden: As graphically as it recounts the horrors of the past, Unforgotten is less concerned with raking the coals of an old scandal than with showing how the treatment of the mentally disabled has since improved.

The film ... focuses on the lives of two who were once incarcerated at Willowbrook but subsequently flourished in group homes situated in close proximity to their families.

/ In looking at the lives of Patty Ann Meskell and Luis Rivera (who died shortly after the film was completed), both of whom spent many years at Willowbrook, the movie stresses their essential humanity.

/ The film, narrated by Danny Aiello, isn't so much an investigative documentary as a blunt plea for the humane treatment of the mentally disabled.

[20] Willowbrook State Hospital is mentioned in the 2009 documentary movie Cropsey as having reportedly housed convicted child kidnapper Andre Rand, who had previously worked there as an orderly.