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 restrictive facility in the federal prison system is
USP Florence ADMAX, the federal
supermax prison, which holds inmates who are considered the most dangerous and in need of the tightest controls. USP Leavenworth, USP Lewisburg, USP Lompoc, and USP Marion were originally operated as high-security facilities but have since been downgraded to medium-security facilities (former USP Lompoc has again been downgraded, to low-security). USP Atlanta, also a former high-security facility, is presently a low-security facility with the primary purpose of holding inmates until they are transferred to other institutions. In 2024, all former USP facilities were renamed to FCI facilities to more accurately reflect their security level. Many current USPs include minimum-security satellite camps on the same property and under the same administration as the higher-security units. == Federal correctional institutions ==