Most United States Penitentiaries (USPs) are high-security facilities, which have highly secured perimeters with walls or reinforced fences, multiple and single-occupant cell housing, the highest staff-to-inmate ratio, and close control of inmate movement. The most notable facility in the federal prison system is Florence ADX, the federal supermax prison in Florence, Colorado which holds inmates who are considered the most dangerous and in need of the tightest controls. USP Atlanta, USP Leavenworth, USP Lompoc, and USP Marion are medium-security facilities. USP Marion contains a highly restrictive Communication Management Unit, which holds inmates under stricter controls.
Federal Correctional Institutions (FCIs) are medium-security and low-security facilities, which have strengthened perimeters (often double fences with electronic detection systems), mostly cell-type housing, a wide variety of work and treatment programs, as well as a higher staff-to-inmate ratio and greater internal controls than low-security FCIs. FCI Terre Haute contains a more restrictive section designated as a Communication Management Unit for inmates considered high-security risks.
Federal Prison Camps (FPCs) are minimum-security facilities, which have dormitory housing, a relatively low staff-to-inmate ratio, and limited or no perimeter fencing. These institutions are work- and program-oriented; and many are located adjacent to larger institutions or on military bases, where inmates help serve the labor needs of the larger institution or base.
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), and Federal Medical Centers (FMCs), as well as the Federal Transfer Center (FTC), the Medical Center for Federal Prisoners (MCFP), and the Administrative-Maximum (ADX) U.S. Penitentiary. Administrative facilities, except the ADX, are capable of holding inmates in all security categories.
A number of BOP facilities belong to Federal Correctional Complexes (FCCs). At FCCs, facilities with different missions and security levels are located in close proximity to one another. FCCs increase efficiency through the sharing of services, enable staff to gain experience at facilities of differing security levels, and enhance emergency preparedness by having additional resources within close proximity.