The famous inmates at ADX Florence, the only federal supermax prison in the United States, include some of the most notorious terrorists, cartel leaders, spies, and gang figures ever prosecuted in this country. The facility in Florence, Colorado holds people the Bureau of Prisons considers too dangerous, too influential, or too great an escape risk for any other institution, and no one has ever escaped from it. The names below give a sense of who ends up there and why.
Terrorists Convicted of Attacks on the United States
The largest and most recognized group at ADX Florence is made up of people convicted of terrorism. Their cases stretch across three decades of attacks on American soil and against American targets abroad.
International Terrorism
Ramzi Yousef is serving life plus 240 years for masterminding the 1993 World Trade Center bombing, which killed six people and injured more than a thousand.1United States Department of Justice. Eric Robert Rudolph Sentenced to Life in Prison for Birmingham Bombing Attack
Zacarias Moussaoui, the only person convicted in a U.S. court in connection with the September 11 attacks, is serving six life terms without the possibility of parole. His sentence was structured as two consecutive life sentences on the lead count and five concurrent life terms on the remaining counts, following his guilty plea to conspiracy charges.
Dzhokhar Tsarnaev, who carried out the 2013 Boston Marathon bombing with his brother, was sentenced to death and transferred to ADX Florence. His death sentence has been the subject of ongoing appeals, including an order from a federal appellate court directing the trial judge to investigate claims of juror bias. Regardless of how those appeals resolve, he will spend the rest of his life in prison.
Richard Reid, the British citizen who tried to detonate a shoe bomb on a transatlantic flight in December 2001, is serving three life sentences plus 110 years. Umar Farouk Abdulmutallab, who attempted to blow up a Detroit-bound flight on Christmas Day 2009 using explosives hidden in his underwear, received four life terms plus 50 years.
Domestic Terrorism
Eric Rudolph pleaded guilty to the 1996 Centennial Olympic Park bombing in Atlanta, which killed a spectator and injured more than a hundred people, along with bombings at a family planning clinic and a nightclub. His plea deal spared him the death penalty in exchange for multiple life sentences without parole.2Department of Justice. Eric Robert Rudolph Sentenced to Life in Prison for Birmingham Bombing Attack3Federal Bureau of Investigation. Eric Rudolph
Terry Nichols, who helped plan and prepare the 1995 Oklahoma City bombing that killed 168 people, is serving 161 consecutive life sentences without parole. That total reflects one life sentence for each murder count at the state level, imposed on top of his federal convictions for conspiracy and involuntary manslaughter.
Heads of Transnational Drug Cartels
Cartel leaders end up at ADX Florence because their wealth and organizational reach make corrupting guards and running operations from behind bars a realistic threat at any lower-security facility.
Joaquín “El Chapo” Guzmán, former head of Mexico’s Sinaloa Cartel, was sentenced in 2019 to life plus 30 years for leading a continuing criminal enterprise that included 26 drug-related violations and a murder conspiracy. The court also ordered $12.6 billion in forfeiture.4United States Department of Justice. Joaquin “El Chapo” Guzman, Sinaloa Cartel Leader, Sentenced to Life in Prison Plus 30 Years Guzmán had already escaped from two maximum-security Mexican prisons before his final capture and extradition to the United States. He has filed complaints alleging severe sleep deprivation and inadequate medical care inside ADX, and he remains housed there.
Osiel Cárdenas Guillén, former head of the Gulf Cartel, was extradited from Mexico in 2007 and pleaded guilty to drug trafficking, money laundering, and threatening to assault and murder federal agents. He received a 25-year sentence and forfeited $50 million. Unlike most inmates on this list, he completed his sentence: he was released from federal prison in August 2024 and deported to Mexico that December, where Mexican authorities re-arrested him on arrival.5U.S. Immigration and Customs Enforcement. Former Leader of the Gulf Cartel Removed After Being Released From Prison
Spies Who Betrayed the United States
Convicted government spies carry classified information that could still cause damage if passed to foreign intelligence services. The soundproofed cells and monitored communications at ADX Florence make it the default destination for these inmates.
Robert Hanssen, a former FBI agent, sold classified information to the Soviet Union and later Russia across roughly 15 years. The FBI has called his case the most damaging espionage in Bureau history.6Federal Bureau of Investigation. Robert Hanssen He pleaded guilty and was sentenced to life in prison without parole under an agreement that spared him the death penalty.7Department of Justice. Hanssen Pleads Guilty to Espionage Hanssen died at ADX Florence on June 5, 2023.
Harold Nicholson, a former CIA officer, was convicted in 1997 of conspiracy to commit espionage for selling classified information to Russia’s foreign intelligence service.8United States Department of Justice. Imprisoned Spy Sentenced to 8 More Years for Conspiracy to Act as an Agent of the Russian Government and Money Laundering He later tried to continue spying from prison by recruiting his own son to collect payments from Russian agents on the outside, which earned him an additional eight years on top of his original sentence.
Prison Gang Leaders and Violent Inmates
Some ADX inmates were not sent there for the crime that originally put them in federal prison. They earned placement by committing murders, directing organized violence, or running criminal operations from inside other penitentiaries.
Tyler Bingham, a high-ranking member of the Aryan Brotherhood, was convicted of murder, racketeering, and conspiracy for directing violent attacks and criminal operations across multiple federal prisons. After a jury deadlocked on the death penalty, he was sentenced to life without parole. His case was part of a broader federal prosecution aimed at dismantling the Aryan Brotherhood’s leadership.
Thomas Silverstein’s name is inseparable from the history of ADX itself. After entering the federal system on a bank robbery conviction, Silverstein killed two fellow inmates and then, in 1983 at the federal penitentiary in Marion, Illinois, stabbed a correctional officer to death. That murder triggered a permanent lockdown at Marion that lasted 23 years and led directly to the construction of ADX Florence as a purpose-built supermax. Silverstein spent more than 36 years in extreme isolation and died on May 11, 2019, at age 67. A federal appeals court had earlier acknowledged that 30 years in solitary was “an extraordinary length of time” but upheld his confinement given his history of lethal violence.
Other Well-Known Figures
Ted Kaczynski, the “Unabomber,” spent years at ADX Florence after pleading guilty to a 17-year mail bombing campaign that killed three people and injured 23 others. He was later transferred to a federal prison medical center in Butner, North Carolina, as his health declined, and died there by suicide on June 10, 2023, at age 81.
Larry Hoover, founder of the Gangster Disciples street gang, is serving six life sentences at ADX Florence. Michael Swango, a former physician who poisoned patients and colleagues, received three life terms.
How Someone Ends Up at ADX Florence
Placement at ADX Florence is not part of a judge’s sentence. The Bureau of Prisons decides administratively, based on an inmate’s behavior, security threat level, and ability to direct criminal activity from behind bars. An inmate who orchestrates violence at a lower-security facility, attempts escape, or holds enough outside influence to endanger the public can be transferred there regardless of the original crime.
Many ADX inmates are also subject to Special Administrative Measures, restrictions the Attorney General can authorize when an inmate’s communications pose a risk of violence or terrorism. Under these measures, the Bureau of Prisons can limit phone calls, mail, and visits to immediate family, and every communication is monitored in real time by the sponsoring law enforcement agency, typically the FBI.9eCFR. 28 CFR 501.3 – Prevention of Acts of Violence and Terrorism A separate provision covers inmates who possess classified information, allowing restrictions designed to prevent disclosure of intelligence secrets.10eCFR. 28 CFR 501.2 – National Security Cases Even books and magazines sent to inmates under these measures must be jointly reviewed by the Bureau of Prisons and the FBI before delivery.11Office of the Inspector General. Audit of the Federal Bureau of Prisons’ Monitoring of Inmate Communications to Prevent Radicalization
Inside the facility, inmates spend roughly 23 hours a day alone in soundproofed concrete cells measuring about seven by twelve feet, with poured concrete furniture and a narrow slit window angled toward the sky. Meals arrive through a slot in the cell door. Recreation is about one hour a day in a slightly larger concrete enclosure. Social visits for inmates in the special housing unit take place by non-contact video, limited to two hours on weekends and federal holidays.12Federal Bureau of Prisons. Visiting Regulations for FCC Florence For inmates serving life without parole for terrorism, or living under Special Administrative Measures, those conditions are effectively permanent.