New Hampshire's Corrections Department says a federal audit of the men's prison in June concluded the prison met or exceeded all 45 standards required under the law.
The audit included all of the housing, programming and treatment units located on the grounds of the prison.
Standards included security of the physical plant; supervision and monitoring of people in the department's custody; and access to medical and mental health care.
The auditor interviewed individuals in the prison's care and custody, employees who work the units, administrators, and division directors.
Each state corrections facility is audited every three years.
The prison also was in compliance in its 2015 audit.