The silent system of Eastern State Penitentiary in the 19th century was conducive to rehabilitation.

Though the silent system was discontinued pretty much everywhere by early in the last century, the reports of recidivism rates we have from its use suggest a rate of less than 10%, as noted by Skotnicki (2000):

“Prior to the Civil War, the rates of reconviction were consistently less than 10%, with the data from the Eastern Penitentiary being the lowest.”

Skotnicki, A. (2000). Religion and the Development of the American Penal System. New York: University Press of America. (p. 145)

This article from Governing examines the system.

An excerpt.

Nearly 185 years ago, several Philadelphia men took up residence in an imposing stone structure in Cherry Hill, a pastoral setting just two miles from the city center. There, they would spend an average of two or three years alone, in complete meditative silence. With only a bed and a Bible, each was expected to devote every waking hour to self-contemplation and his relationship with God.

But this was no monastery and these were not monks. They were the first prisoners admitted to the Eastern State Penitentiary, which began construction in 1821 and opened eight years later. Architect John Haviland was instructed to “convey to the mind a cheerless blank indicative of the misery which awaits the unhappy being who enters within its walls.” With its 80-foot bell tower, 30-foot walls and 27-foot-tall iron-studded oak doors, the building resembled a massive fortress. The only larger building in the country at the time was the U.S. Capitol.

As foreboding as it was, Eastern State was designed from the beginning to implement new, more humane theories about crime and punishment. Presaging many of today’s arguments on corrections reform, the emphasis was much less on punishment and more on rehabilitation. Philadelphians, drawing on their Quaker roots, had long argued for better treatment of prisoners. They believed that if prisoners were left alone in complete silence, with nothing to occupy their minds but thoughts of their misdeeds, they would become genuinely penitent. (Hence, the building was known as a “penitentiary.”)

The place was utterly silent. Guards walked the halls with socks over their shoes. The wheels on the wagons that brought food down the long corridors were covered in leather. For 23 hours of every day, inmates were confined to a 7.5- by-12-foot cell with a church-like vaulted ceiling and small skylight. For the remaining hour they were allowed outside within their own small exercise area. Inmates in adjoining cells were never allowed outside at the same time, and any communication between prisoners was strictly forbidden.

Retrieved April 13, 2014 from http://www.governing.com/topics/public-justice-safety/gov-prison-sounds-of-silence.html