There is only one federal supermax prison in the United States: ADX Florence in Florence, Colorado, which is the most secure federal facility housing the most dangerous and high-profile inmates

. However, many states operate their own supermax prisons or supermax units within other prisons. By 2006, 44 states had at least one supermax facility

. Examples of state supermax prisons include Pelican Bay State Prison in California and Tamms Correctional Center in Illinois

. In summary:

• Federal system: 1 supermax prison (ADX Florence)
• State systems: Numerous supermax prisons or units across at least 44 states, with some states having multiple facilities

The exact total number of state supermax prisons fluctuates as facilities open, close, or are repurposed, but supermax prisons are a significant part of the U.S. correctional landscape beyond the single federal supermax.