The jail in Valhalla has nearly 1,700 beds and about 900 uniformed and civilian employees.
The study found a pattern of excessive force at the jail, resulting in serious harm to inmates. It said the use of excessive force and the deprivation of basic medical care was particularly disturbing, while the jail's treatment of juveniles raised serious constitutional concerns.
The Justice Department says it will work with Westchester County officials to resolve the issues. A message left with the office of the county attorney was not immediately returned.