The hospital confined and treated individuals who were committed to it by criminal courts and who were declared insane while serving their sentences at state institutions.

The site was rural, yet accessible by rail and offered good tillable land, pure water and pleasant scenery between the Hudson River and the Fishkill Mountains.

Architect Isaac Perry, known for finishing work on the New York State Capitol, was hired to design the main hospital building with "an abundance of light and ventilation" to accommodate 550 patients.

These included a tool shed built in 1900, a greenhouse (1919), a large residence hall for male patients and staff assigned to work the farm (1932) and a horse stable (1933).

Patients played softball, tennis, bowling, handball, shuffleboard, volleyball, chess, checkers, cards, gymnastics, ping pong and quoits.

[2] The hospital's cemetery, which includes the remains of nearly 1,000 patients that died there, is just west of Beacon High School on Matteawan Road.

[2] Some buildings from the former Matteawan State Hospital for the Criminally Insane now serve as part of the medium-security Fishkill Correctional Facility.