The idea that depriving a person of his freedom could serve as punishment for a crime is comparatively new. Political offenders were often kept in prison for long lengths of time, but criminals would normally stay in jail only a short time before receiving capital or corporal punishment. The earliest prisons contained mainly paupers and debtors, but also some petty criminals as well. They were commonly called debtor's prisons or houses of correction. One of the earliest was Bridewell, opened in 1557 in London.

By the 18th century, houses of correction had developed into places where criminals were sent for lengthy terms as a means of punishment. They were housed with the poor without regard to sex, age, or type of crime. The houses of correction became notorious for foul conditions and vice.

In 1704 Pope Clement XI established in Rome a house of correction for juvenile offenders only, separating boys from hardened criminals. Cesare Beccaria (1738?-1794), an Italian criminologist, published a book in 1764 urging prison reform.

In 1771 a house of correction was built in Ghent, Belgium, that influenced architecture and management of prisons into the 20th century. The building was octagonal, with individual cells facing inward. Prisoners were classified and separated by sex and offense, and were given training in useful trades.

In Great Britain during the latter 18th and early 19th century, John Howard, Jeremy Bentham, and Elizabeth Gurney Fry were leaders in prison reform. Penitentiaries were built to house prisoners in separate cells. In 1869 Great Britain stopped imprisoning debtors and paupers.

After a policy of harsh treatment for prisoners had been followed from 1865 to 1895, a system emphasizing training was adopted. In 1908 Parliament established a system of treating youthful offenders outside the prisons in training institutions called Borstals after the village where the first one was located.

In the colonial period the Quakers were in the forefront of progress in penology. In 1682 in Pennsylvania William Penn abandoned the death penalty for all offenses except murder. Imprisonment was adopted as the chief punishment for crime. In 1718, however, the British government imposed on Pennsylvania much of the harsh English penal code.

After independence was declared in 1776 Pennsylvania made a series of reforms. Imprisonment was again adopted as the punishment for crime. Walnut Street Jail in Philadelphia became the first prison in the United States. Pennsylvania developed the solitary, or separate system. Each prisoner was locked up alone in a cell to meditate and to do penance for his or her sins—hence the name “penitentiary.”

In 1825 the Auburn Prison in New York adopted the silent system. Prisoners were confined in separate cells at night but worked together by day in a prison factory under enforced silence. With its prison factory Auburn became a profitable enterprise, and for this reason was widely copied in many states.

Another step was the founding in 1876 of the first state reformatory, in Elmira, New York. The early reformatories, however, were little different from prisons, and not until after 1925 were most such institutions designed and equipped for rehabilitation. At the same time reformatory principles began to be applied in some traditional prisons. After World War II the federal government and some states experimented with medium-and minimum-security prisons for convicts who did not need close confinement.

Until the 20th century the federal government arranged to have its prisoners confined in state prisons and county jails. The first two federal penitentiaries (at Leavenworth, Kansas, and Atlanta, Georgia) opened in 1905. The Bureau of Prisons was organized in 1930. In 1963 the famous federal prison on Alcatraz Island, San Francisco Bay, was closed and replaced by the new maximum-security prison in Marion, Illinois.

In the 1970's, inmates rioted in institutions in many parts of the country protesting prison conditions and seeking expansion of prisoners' rights. In the late 1970's and early 1980's, after a series of federal court orders requiring the states to expand and upgrade their prison facilities, many of the worst abuses and conditions were eliminated.

Overcrowding continued to be a problem in most states throughout the 1980's. To handle the problem, lawmakers provided for shorter sentences for certain crimes, and prison authorities began releasing many prisoners before their terms expired. States also worked at providing alternatives to prison sentences, such as putting nonviolent criminals under house arrest in their own homes or placing them in halfway houses. For first-time offenders several states established “boot camps,” facilities in which prisoners serve 90-day terms with military-style discipline, marching drills, calisthenics, and hard labor.

To offset the rising costs of incarcerating prisoners, many states and counties passed laws in the 1990's that allowed prisons to charge inmates for some of these costs. Also during the 1990's there was an increase in the number of prison-work programs.