While surfing for interesting photo archives online, I discovered the Correctional Photo Archives. From the site:
The American Prison Society Photographic Archive records collection was acquired by the Eastern Kentucky University Archives in 1984 through the auspices of Dr. Bruce Wolford of Eastern's College of Law Enforcement. Dr. Wolford received the photographs in 1979 from William Bain, instructor at the Kentucky Bureau of Training. In the 1960s Mr. Bain, a former staff member of the American Correctional Association, conceived the idea of a pictorial history of the American prison. With the aid of David A. Kimberling, a prison inmate and photographer, Bain had photographs copied from the American Correctional Association archives plus ones he received from various federal and state correctional facilities throughout the United States. In addition to the copies, which comprise the negative part of the collection, he acquired many original black and white photographic prints. Finally in 1978 through the work of Anthony P. Travisono, executive director of the American Correctional Association, Bain's dream, The American Prison: from the Beginning. A Pictorial History, was published.
The photographic collection is rich in its depiction of early twentieth century prison life and conditions. The collection covers numerous subjects such as prison living conditions, recreational activities, industries, hospital care, corporal punishment, work gangs on the farm and quarries, vocational activities, weapons confiscated, prison architecture, and the death house. A few of the images are of prison officials, primarily in the federal penitentiary system.
A source of contemporary prison photographs is Richard Ross's Architecture of Authority and its online gallery.