Pilgrim Psychiatric Center opened in 1931 with a comprehensive mental health campus that was the largest of its kind at the time. It included a farm, post office, power plant, courtrooms, and even a fire department along with its hospital and cemetery. Yet by the late 1990s it had fallen into heavy disrepair.

At its peak in 1954, the hospital served a population of more than 13,000 patients. Currently, Pilgrim State Hospital is the only large mental health institution active for Nassau and Suffolk counties. There are 15 inpatient wards including three admission wards, three geriatric wards, and nine psychiatric rehabilitation wards which include two behavioral treatment wards. Some areas remain closed. Police are a regular presence.

A museum in the new Pilgrim State Hospital called the Long Island Psychiatric Museum is open to the public, and hold artifacts related to the history of all three Long Island hospitals: Kings Park, Central Islip, Pilgrim.