The types of prisons in the United States fall into a handful of clear categories: local jails, state prisons, federal prisons, private facilities operated under government contract, immigration detention centers, military prisons, and juvenile detention facilities. Within those categories, individual institutions are further sorted by security level, from open-dormitory camps to the single administrative-maximum penitentiary in Florence, Colorado. Roughly 1.8 million people are held across the whole system on any given day, and which facility someone lands in depends on who prosecuted them, what they were convicted of, and how a classification score reads their risk.
Jails vs. Prisons
The most common source of confusion is the line between a jail and a prison. Jails are run locally — by cities, counties, or regional authorities — and hold two populations: people awaiting trial who haven’t been convicted of anything, and people serving short sentences after a misdemeanor conviction. About 70 percent of the people in jail on a given day are in pretrial detention, usually because they couldn’t post bail.
Prisons are run by state or federal governments and hold people convicted of felonies serving sentences longer than one year. Someone sentenced to eight months for a misdemeanor goes to jail. Someone sentenced to five years for a felony goes to prison. The prosecuting jurisdiction decides which system you enter: a federal conviction sends you to the Federal Bureau of Prisons, and a state conviction sends you into that state’s correctional department.
Federal Prison Security Levels
The Federal Bureau of Prisons assigns inmates to facilities using a point-based scoring system that weighs offense severity, criminal history, violence history, escape risk, age, and other factors. Under 18 U.S.C. § 3621, the Bureau has sole authority to designate where a federal prisoner serves a sentence. A sentencing court can recommend a placement, but the recommendation is not binding.1Office of the Law Revision Counsel. 18 USC 3621 – Imprisonment of a Convicted Person
The resulting score, combined with any applicable public safety factors, maps to one of five categories.2Federal Bureau of Prisons. Inmate Security Designation and Custody Classification
Minimum Security (Federal Prison Camps)
Federal Prison Camps use dormitory housing with limited or no perimeter fencing and a low staff-to-inmate ratio. They lean heavily on work assignments and programming, with inmates maintaining grounds, working in kitchens, or taking education courses. The population consists of people with the lowest security scores, often serving shorter sentences for nonviolent offenses.3Federal Bureau of Prisons. Federal Prisons
Low Security
Low security Federal Correctional Institutions use double-fenced perimeters and mostly dormitory or cubicle housing. Staff presence is higher than at camps, and work and programming remain central. These facilities hold people whose scores are above the camp threshold but who don’t require cell-based housing.
Medium Security
Medium security institutions use stronger perimeters, often double fences with electronic detection, and house inmates in cells rather than open dormitories. Movement is more tightly controlled, and the population typically includes people with longer sentences or histories of violence that push their scores into the middle range.
High Security (U.S. Penitentiaries)
United States Penitentiaries use walls or reinforced fences, single- or multiple-occupancy cells, the highest staff-to-inmate ratio in the system, and close control of all movement. The population includes people convicted of serious violent crimes and those with the highest security point totals. These are the facilities most people picture when they hear “federal prison.”
Administrative Facilities
Administrative facilities sit outside the standard security ladder because they serve specialized missions. The category includes Metropolitan Detention Centers for pretrial defendants, Federal Medical Centers for inmates with serious health conditions, the Federal Transfer Center that coordinates prisoner movement, and the Administrative-Maximum Security Penitentiary (ADX) in Florence, Colorado. ADX is the most restrictive facility in the federal system; inmates there spend roughly 23 hours a day alone in a cell with severely limited human contact. Apart from ADX, administrative facilities can hold inmates of any security level.
Security designations are not permanent. A unit team of case managers, counselors, and other staff periodically reviews each inmate’s classification. Clean conduct, completion of programming, and the passage of time can lower a score and open the door to transfer to a less restrictive facility.4Federal Bureau of Prisons. Inmate Classification and Program Review
State Prisons
Each state runs its own prison system under its own penal code, so security labels, facility names, and programming vary from state to state. The common pattern is that new arrivals go through a reception and classification center for psychological and physical evaluation, and the results drive facility assignment. Most states operate facilities across the minimum-to-maximum range, though they define those tiers on their own terms.
State systems hold far more people than the federal system. Roughly 1.1 million people are in state prisons at any given time, compared with about 155,000 in federal custody. Many states organize their facilities by geographic region to keep incarcerated people closer to their families, which research links to better outcomes after release.
Most states also operate reduced-custody options. Honor farms, work release centers, and transitional facilities give inmates with clean disciplinary records a chance to work outside the walls in exchange for less physical security; violations send participants back to a higher-security facility. Community corrections centers go a step further, placing inmates in a structured residential setting with curfews, drug testing, job placement, and treatment services. The federal system runs the same model under the name Residential Reentry Centers, typically used in the final months of a sentence.5Department of Justice Office of the Inspector General. DOJ OIG Releases Report on BOP’s Use of Residential Reentry Centers and Home Confinement
Private Prisons
Private prisons are operated by for-profit corporations under contract with federal or state governments. About 8 percent of the combined state and federal prison population — roughly 90,000 people — is held in privately run facilities. CoreCivic and the GEO Group are the two dominant companies, together managing more than half of all private prison contracts in the country.
The arrangement is straightforward. The government pays the corporation a daily rate per inmate, and the corporation handles staffing, food, medical care, and security with its own employees. The government keeps legal custody; only day-to-day operations are outsourced. Many contracts include occupancy guarantees requiring that a minimum share of beds stay filled.
Federal policy on private prisons has moved back and forth. A January 2021 executive order directed the Department of Justice to phase out its use of privately operated criminal detention facilities. That order was revoked in January 2025, restoring the Bureau of Prisons’ authority to contract with private operators.6The White House. Initial Rescissions of Harmful Executive Orders and Actions The Bureau monitors federal private facilities through a Contracting Officer’s Representative assigned to each site, on-site reviews by subject-matter experts, and financial deductions when contractors fail to deliver required services.7Federal Bureau of Prisons. Oversight of Private Secure Correctional Facilities
Immigration Detention Facilities
Immigration detention operates on a different legal footing than criminal incarceration. People in immigration custody are being held civilly while the government processes removal proceedings or prepares deportation; they are not serving a criminal sentence. The buildings often look like jails or prisons, but the basis for confinement is administrative.
U.S. Immigration and Customs Enforcement uses three main facility types. Service Processing Centers are owned and operated directly by ICE. Contract Detention Facilities are run by private companies under ICE contracts. The third and largest category is state and local jails that hold immigration detainees under Intergovernmental Service Agreements with ICE.8U.S. Immigration and Customs Enforcement. Custody Classification System
Detainees have the right to immigration court hearings but generally do not have a constitutional right to appointed counsel, a significant practical difference from criminal defendants.
Military Prisons
Service members convicted by courts-martial under the Uniform Code of Military Justice serve their sentences in military correctional facilities rather than civilian prisons. A military tribunal adjudicates the case, and confinement can be carried out in any facility under the control of the armed forces or in a federal penal institution.9Office of the Law Revision Counsel. 10 USC 858 – Art 58 Execution of Confinement
The United States Disciplinary Barracks at Fort Leavenworth, Kansas, is the only maximum-security military prison in the Department of Defense and the oldest federal correctional institution in the country. It holds service members serving long sentences and runs programs aimed at discipline and reducing reoffending after release.10United States Army. Army Corrections Command Each military branch also operates its own lower-security confinement facilities for shorter sentences. Military corrections includes a goal the civilian system doesn’t share: in some cases, returning the service member to duty.
Juvenile Detention Facilities
Minors adjudicated delinquent in juvenile or family courts are held in juvenile detention centers built around rehabilitation rather than punishment. These facilities emphasize education, counseling, and developmental programming, and they are kept physically separate from adult institutions. Roughly 36,000 young people are held across more than 1,200 juvenile facilities nationwide on any given day.
In rare cases, a minor charged with a particularly serious offense can be transferred to adult court and, on conviction, sentenced to an adult facility. The standards vary by state, but transfer generally requires a violent felony and a judicial finding that the juvenile system can’t adequately handle the case.
Rights That Apply Across Every Facility Type
Whatever the facility, incarcerated people retain certain constitutional protections — above all the Eighth Amendment ban on cruel and unusual punishment and the Fourteenth Amendment guarantee of due process. When conditions violate those rights, an inmate can sue in federal court. The Prison Litigation Reform Act adds a mandatory prerequisite: every prisoner must exhaust the facility’s internal grievance procedures before filing suit.11Office of the Law Revision Counsel. 42 USC 1997e – Suits by Prisoners
The exhaustion rule applies in federal prisons, state prisons, local jails, and private facilities alike. The Supreme Court has recognized a narrow exception for cases where the grievance process is genuinely unavailable — for example, when staff block access to it or when the procedure is so confusing that no reasonable person could use it. Inmates who skip the process and head straight to court usually see their cases dismissed, even when the underlying claim has merit.