There are 122 Federal Bureau Prisons (BOP) in the United States. These institutions range from Minimum-security to High-security facilities throughout the U.S. with one Administrative-Maximum facility (ADX) in Florence, Colorado. Institutions are operated at five different security levels to confine offenders in an appropriate manner. Security levels are based on such features as the presence of external patrols, towers, security barriers, or detection devices; the type of housing within the institution; internal security features; and the staff-to-inmate ratio. Facilities are designated as either minimum, low, medium, high, or administrative; and facilities with different security levels that are near each other are known as prison complexes.
As of September 6, 2025, there were 154,903 federal inmates in the United States. The federal prison system “officially” startedunder the Three Prisons Act (1891), which authorized the first three federal penitentiaries: United States Penitentiary (USP) Leavenworth, USP Atlanta and USP McNeil Island. However, some argue the first federal prison was the famed “Alcatraz” facility on an island near San Francisco and the Golden Gate Bridge. Alcatraz started by housing military prisoners in the late 1850’s but was not turned over to the BOP until 1933.
Dr. Mischel, retired U.S. Department of Justice employee –Federal Bureau of Prisons Psychologist and Associate Warden spoke to the Frankfort Rotary Club in August. The “behind the scenes” realities of the prison system and its security levels are not something most of us think much about, but these realities are lived by over 150,000 inmates in the United States every day.
The federal prison system can be divided into the following security levels followed by the percentage of the federal prison population for each group.
Minimum Security: There are seven minimum security confinement facilities in the federal system. Minimum security institutions, also known as Federal Prison Camps (FPCs), have dormitory housing, a relatively low staff-to-inmate ratio, and limited or no perimeter fencing. These institutions are work- and program-oriented. Several BOP institutions have a small, minimum–security camp adjacent to the main facility. These camps, often referred to as Satellite Prison Camps (SCPs), provide inmate labor to the main institution and to off-site work programs.
These facilities are often small dormitory-like settings and may sometimes be hard to even recognize as prisons since minimum security facilities may be in residential areas with no fences or barbed wire. Those inmates who decide not to stay within the confines of the designated areas are affectionately referred to as “walk-away” as it is not an “escape” to cross the road. Walking away, however, may be a great way to add several years to a sentence. These minimum–level facilities are for non-violent offenders with under 10–year sentences who may be guilty of certain possession or distribution crimes, white collar crimes such as fraud, embezzlement, money laundering, or mail fraud. At minimum-security level federal prisons, it may even be possible to check out to visit family and return at a pre-determined time – a furlough. Only about 14% of federal inmates are housed in minimum security prisons.
Low Security: There are 24 low–level federal correctional institutions (FCIs) in the U.S. Low security prisons are characterized by double-fenced perimeters, mostly dormitory or cubicle housing, and strong work and program components. The staff-to-inmate ratio in these institutions is higher than in minimum security facilities. Offenders in low security prisons are often there for drug offenses, white collar crimes, identity theft, some sex offenses, and some immigration violations. Many offenders in low security prisons are first time offenders.
As security levels increase, moves throughout the prison become more controlled.
Medium Security: About 32 percent of all federal inmates are housed in medium security facilities. Medium security FCIs(and USPs designated to house medium security inmates) have strengthened perimeters (often double fences with electronic detection systems), mostly cell-type housing, a wide variety of work and treatment programs, an even higher staff-to-inmate ratio than low security FCIs, and even greater internal controls. These inmates may have extensive criminal histories and pose a greater risk level than those in minimum or low-security level prisons. Inmates are typically housed in secure, two-person cells. Buildings may include a library and space for religious services but movement between areas is more controlled and restricted than lower-level prisons. It is not unusual for inmates in medium security prisons to have sentences up to 20 to 30 years.
High Security: High security institutions, also known as United States Penitentiaries (USPs), have highly secured perimeters (featuring walls or reinforced fences), multiple- and single-occupant cell housing, the highest staff-to-inmate ratio, and close control of inmate movement. Violent and dangerous offenders are found in high security Federal prisons along with all gang members. Stringent safety measures like controlled inmate movement, stand-up and frequent census counts are conducted throughout the day. As in medium-security facilities, inmates are constantly under surveillance.
Closer to home, USP Terre Haute’s unique mission is to house all federal death row inmates. Mischel said it is more expensive to execute an inmate than it is to house them for the rest of their life. This is due to the cost of multiple trials and mandatory legal fees incurred in the death row process because two separate legal teams are required to represent death row inmates.
Complex: At Federal Correctional Complexes (FCCs), institutions with different missions and security levels are near one another. FCCs increase efficiency through the sharing of services, enable staff to gain experience at institutions of many security levels, and enhance emergency preparedness by having additional resources within close proximity.
Administrative Security: Administrative facilities are institutions with special missions, such as the detention of pretrial offenders; the treatment of inmates with serious or chronic medical problems; or the containment of extremely dangerous, violent, or escape-prone inmates. Administrative facilities include Metropolitan Correctional Centers (MCCs), Metropolitan Detention Centers (MDCs), Federal Detention Centers (FDCs), Federal Medical Centers (FMCs), the Federal Transfer Center (FTC), the Medical Center for Federal Prisoners (MCFP), and the Administrative-Maximum Security Penitentiary (ADX). Administrative facilities, except the ADX, can hold inmates in all security categories.
The most extreme example of High Security is the ADX in Florence, Colorado. A facility for the most dangerous and violent individuals. There are about 475 inmates housed in single occupancy cells in this facility, spending upwards of 23 hours a day in their cell. Single-cell occupancy does notconstitute solitary confinement in the BOP. Inmates interact with staff from all departments throughout their day and receive recreation time outside their cell.
Of Interest: The average cost of feeding inmates is about $3.00 per day per inmate. This may vary slightly on region and number of inmates on specialized diets.
Only seven percent of federal inmates are female and they are housed in 29 facilities. Female inmates are usually classified as minimum or low security with approximately 10 inmates with high security classification.
Constitutionally protected religious services in the federal prison system result in as many as 24 different types of religious services including ceremonies involving Eagle Feathers and Sweat lodge procedures, prayer rugs, certified religious diets, ceremonial meals, and other accommodations as required per religion.
Transgender inmates in the federal prison system are now, by executive order, determined by assignments based on sex at birth. Prior to the executive order, BOP policy handled transgendered inmates on a case–by–case basis. Notably, no female to male transgender inmates were ever housed in a male federal prison, according to available information.
Since the federal prison system started in 1930, only 27 federal correctional workers have been killed in the line of duty. Making it one of the safest law enforcement jobs in the U.S.
