Pilgrim State Hospital - "originally designed to house 12,500 patients on 1900 acres of land" - constructed from 1930-1941 in Brentwood, New York, USA. " . . . holds the record of being the largest psychiatric hospital in the world" when population peaked at 16,000.
Pilgrim State Hospital, Brentwood, NY, 1938. A mental patient strapped into a continuous-flow tub. This method was used to calm down the patient. Their bodies were greased, which enabled them to remain in the tub for hours and gradually fall asleep.