The World’s Most Secure Buildings: ADX Florence Prison

ADMAX Florence United States Penitentiary, also known as ADX Florence, Florence ADMAX, Supermax, or the Alcatraz of the Rockies, is an administrative maximum-security penitentiary located in Fremont County near Florence, Colorado. It is operated by the Federal Bureau of Prisons, a division of the U.S. Department of Justice.

ADX Florence Prison

Opened in 1994, USP ADX Florence is categorized as a supermax or control unit prison, which provides a higher, more controlled level of custody than a maximum-security prison.

Supermax prisons are designed to hold inmates that pose extreme security threats. Prisoners have little to no time outside of their cells, very few activities, and very little contact with other humans. ADX Florence is considered to be an early example of what would become the supermax model.

ADX Florence Prison forms part of the Federal Correctional Complex in Florence (FCC Florence), which is situated on 49 acres of land and houses various facilities with differing degrees of security. It was commissioned when the Federal Bureau of Prisons needed a unit designed specifically for the secure housing of those prisoners most capable of extreme, sustained violence toward staff or other prisoners.

What makes ADX Florence Prison one of the world’s most secure buildings? Read on to find out.

ADX Florence Prison

A Brief History of ADX Florence Prison

ADX Florence was created after severe incidents occurred at other federal prisons. For instance, at Marion U.S. Penitentiary in 1983, there were two violent incidents where correction officers were stabbed to death. As a result of such ruthless prisoner attacks came the necessity for higher level security prisons.

Some of the most dangerous and notable criminals in the United States have been incarcerated at ADX Florence. The prison holds criminal leaders of a variety of violent gangs, along with domestic and international terrorists from major organizations like Al Qaeda.

ADX Florence Prison Interior

Zacarias Moussaoui, who happens to be the only person convicted in a civilian court for the terrorist attacks on 9/11, is currently at ADX Florence. Dzhokhar Tsarnaev, who was partially responsible for the Boston Marathon bombings, was transferred to this prison in July 2015. There are other notable criminals housed there, such as the Unabomber Ted Kaczynski, shoe bomber Richard Reid, Oklahoma City bomber accomplice Terry Nichols, Olympic Park bomber Eric Rudolph, and Soviet spy Robert Hanssen. Overall, ADX Florence houses all sorts of dangerous criminals in one of the most secure environments.

Facilities in ADX Florence Prison

According to SF Gate, ADX Florence is the only prison specifically designed to keep every occupant in near-total solitary confinement. The facility takes up 21 acres of land, holding dangerous male prisoners who require high levels of security. In total, the prison currently has 344 inmates, with a maximum capacity to hold up to 490 prisoners.

For at least the first three years at this facility, prisoners are not allowed to come into contact with other prisoners at any time, anywhere on the premises. Over time, good behavior can earn inmates more “outside” time, and for the most fortunate, a potential transfer back to a less-secure prison can be possible. The outside time is actually a bigger cell with vaulted ceilings called the “concrete pit” or “empty swimming pool”.

ADX Florence Prison diagram

Prison Cells

The majority of the facility is above ground, except for a subterranean corridor that links cellblocks to the lobby. Each supermax prison cell has a desk, stool, and bed, which are almost entirely made out of poured concrete. There is also a toilet that shuts off if blocked, a shower that runs on a timer to prevent flooding, and a sink lacking a potentially dangerous tap. Rooms may also be fitted with polished steel mirrors bolted to the wall, an electric light that can be shut off only remotely, a radio, and a television that shows recreational, educational, and religious shows.

ADX Florence Prison cell diagram

The 4-inch-by-4-foot windows are designed to prevent inmates from knowing their specific location within the complex. They can see only the sky and roof through these tiny window slits, so it is virtually impossible to plan an escape.

ADX Florence Prison concrete pit

Concrete Pit

Prisoners exercise in a concrete pit that looks like an empty swimming pool. It is also designed to prevent them from knowing their location in the facility. The pit is only large enough for a prisoner to walk 10 steps in a straight line or 31 steps in a circle.

Food and Dining

There is no mess hall. Food is hand-delivered to each inmate by the correctional officers. The ADX Florence Prison has a three-year program that keeps inmates in their cells 23 hours a day for the first year, then gradually socializes them with other inmates and staff. In their last year, prisoners can be out of their cells from 6 AM to 10 PM and eat meals in a shared dining room, instead of having food delivered through a slot in their steel cell door.

Education and Recreation

Each facility included in the FCC Florence complex offers various educational opportunities and numerous programs to the inmates. To educate the prisoners, programs such as the General Education Development Program, Adult Continuing Education, Adult Occupational Education, and English as a Second Language are available. Inmates can also take part in vocational training and parenting programs. Religious, food, recreational, medical, and mental health services are provided to the inmates at this facility.

The Recreational Program, in particular, encourages an active lifestyle and allows inmates to take interest in new hobbies and activities. It lines up activities such as team sports, wellness instruction, and crafting for the inmates. Although these programs are available, prisoners are still under 23-hour lock-up in their cells and have only 5 hours of recreation time each week.

ADX Florence Prison cell block

Facts About ADX Florence Prison

  • ADX Florence is a 37-acre complex located at 5880 Highway 67, with a Florence, Colorado postal address
  • It is part of the FCC Florence which consists of three correctional facilities, each with a different security rating
  • As of May 2022, there are a total of 344 inmates housed
  • Prisoners are confined 23 hours per day in single cells with facilities made of poured, reinforced concrete to deter self-harm
  • Prisoners are under 24-hour supervision, carried out intensively with high staff-inmate ratios
  • On average, the prisoners’ ages range from 24 to 77 years old and the average sentence length is 22 years
  • ADX Florence has nine housing units that are encompassed by a secure fence
  • Every cell has a desk, stool, bed, toilet, shower, sink, and sometimes a steel mirror, radio, and electric light
  • On rare occasions, some cells have black and white television for religious and recreational purposes
  • Cells are also soundproof to avoid any contact at all between prisoners
  • The window in each cell is so small that inmates cannot tell where they are by looking out the window, making it nearly impossible to plan an escape
  • An offender can request up to 20 people on their visiting list and any visitors must be an approved member of this list
  • Inmates can have no more than three visitors at once, including children
  • Before entering the visiting room, visitors will are required to clear a metal detector search
  • When prison guards unlock a cell door, they quickly cover their key with an aluminum shield

ADX Florence Prison exterior

What Makes ADX Florence Prison One of the World’s Most Secure Buildings?

ADX Florence Prison as a whole contains a multitude of motion detectors, cameras, and 1,400 remote-controlled steel doors. Officers in the prison’s control center monitor inmates 24 hours a day and can activate a “panic button”, which closes every door in the facility, should an escape attempt happen.

Pressure pads and 12-foot tall razor wire fences surround the perimeter, which is patrolled by heavily armed officers. As an added level of security, laser beams and attack dogs guard the area surrounding the prison’s outlying fences.

ADX Florence Prison fence

The facility houses inmates at six differing security levels:

  1. General Population Units (“Delta”, “Echo”, “Fox”, and “Golf” Units)
  2. Special Housing Unit (SHU)
  3. Special Security Unit (“H” Unit)
  4. Control Unit
  5. Intermediate/Transitional Units (“Kilo” and “Joker” Units)
  6. Range 13

Many of the security levels at ADX Florence have special purposes or missions for the inmates that occupy them. For instance:

  • The Control Unit houses inmates who have committed serious conduct violations or acts of violence at other institutions. It also houses high-level members of organizations that are deemed as threats, such as prison gangs.
  • “H” Unit houses members of designated terror groups by the Department of Justice or inmates who have had special administrative measures (SAMs) placed on them.
  • Range 13 is a special four-cell wing within the Special Housing Unit for inmates who need the tightest control within ADX.

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The World's Most Secure Building