At any given time, nearly 2 million people are behind bars in the United States. That’s one of the highest rates in the world, at roughly 580 per 100,000 residents, according to the nonprofit Prison Policy Initiative.
About 1.1 million inmates are serving time in state prisons, 562,000 are housed in local jails, and 203,000 are locked up in federal prisons and jails, reported the Prison Policy Initiative, a think tank that advocates against mass criminalization and publishes research about incarceration.
Jails and prisons each serve distinct purposes in the U.S. criminal justice system.
Jails Are Short-Term Detention Institutions
Jails are short-term lockups for towns, cities and counties that hold people who are waiting for their trials or serving sentences of less than one year for misdemeanor convictions.
Inmates convicted of more serious crimes may also be held in jails while awaiting transfer to state or federal prisons. Jails sometimes rent cell space to overcrowded state prisons that then send inmates who are sentenced to longer terms to serve their time in jails.
U.S. jails are largely run by county or city governments and managed by local law enforcement authorities, such as sheriff or police departments. A small number of jails are privately operated.
People were sent to jail roughly 7.6 million times in 2023, according to the Bureau of Justice Statistics, an agency under the U.S. Department of Justice. This accounts for the fact that 1 in 4 people who go to jail are arrested again in the same year. The repeat offenders are usually people suffering from mental illness, poverty and substance use disorders.
About two-thirds of the people locked up in jails have not yet been convicted of crimes. People who have been arrested and can afford bail may be confined in jails for just hours or days, while those who cannot are often held until trial.
States frequently house offenders under age 18 in juvenile detention centers rather than jails.
Criminals Convicted of Felonies Go to Prison
In contrast to jails, prisons are state and federally run lockups where people convicted of more serious criminal offenses, almost always felonies, serve sentences of more than a year. The United States has 1,566 state-run prisons and 98 federal prisons, according to the Prison Policy Initiative. In a 2025 report, the group found that 47% of the inmates held in prisons had been convicted of violent crimes, which include rape and sexual assault, murder, robbery and assault.
Experts cite four major purposes of these correctional facilities: retribution (or punishment); deterrence, or discouraging people from breaking the law; incapacitation, or removal of people from society who could harm members of the public; and the rehabilitation of prisoners.
Facilities range from minimum-security prisons for nonviolent offenders to extremely restrictive supermax prisons for inmates who pose significant security risks to the public, corrections officers and other prisoners. Juvenile offenders convicted of crimes are usually held in youth prisons and correctional facilities but some states allow juveniles to be convicted as adults so they serve their sentences in lockups for adults.
Some inmates are sent to private prisons owned by for-profit companies working under contract with government entities. Currently, 28 states house inmates in privately-owned institutions in addition to state-run prisons and local jails.
Jails Tend to be More Chaotic Than Prisons
Jails and prisons equally experience challenges and come under severe criticism for overcrowding, understaffing, inadequate healthcare and poor food quality. While violence is a significant problem at both types of institutions, it can be more unpredictable in jails due to the higher turnover of inmates, causing greater inmate population instability and chaotic lockup conditions.
While long-term correctional institutions hold inmates convicted of very serious crimes, prisons are more likely to offer education, career and rehabilitative services. Some jails offer hospitalization services for people with mental health and substance abuse needs, along with other short-term resources.
While jails and prisons seem similar, the people who run them, how they operate and why they exist differ—and that’s by design.
