The story of the largest lawsuit ever filed against the United States Bureau of Prisons begins, improbably enough, with this letter. Deborah Golden, the director of the D.C. Prisoners’ Project, fields approximately 2,000 requests each year, but Bacote’s, which she received in October 2009, caught her eye. “I thought I might be missing something, because it was inconceivable to me that the Bureau of Prisons could be operating in such a blatantly illegal and unconstitutional manner,” she said. Golden was referring to B.O.P. regulations that forbid the placement of inmates who “show evidence of significant mental disorder” in prisons like the ADX.

Groups like Golden’s D.C. Prisoners’ Project tend to focus their reform efforts on state-run prisons — in part because the Prison Litigation Reform Act, passed by Congress in 1996, made it more difficult for prisoners to file federal lawsuits, and in part because the federal government possesses, as Golden put it, “an inexhaustible supply of resources.” A droll 42-year-old attorney who once considered rabbinical school, Golden has spent her entire career practicing human rights law. As she investigated Bacote’s claims, she came to realize there were dozens of inmates at the ADX with comparable stories, or worse: cases of self-mutilation, obvious psychosis, suicide. Her organization had never considered filing such an enormous suit. Because it is so difficult to win cases against the federal government, challenging the B.O.P. “just didn’t fit into anyone’s strategic goals,” Golden explained. The last major B.O.P. lawsuit to result in a settlement was in the mid-’90s (Lucas v. White, brought by a group of female inmates who had been sexually assaulted). But the clarity of Bacote’s claims gave her pause. “A lot of cases we see involve matters of interpretation: Who knew what and when,” she said. “This didn’t seem to involve that kind of uncertainty. I wasn’t sure if we had a chance. But it seemed like a court had to see it.”

Since opening in 1994, the ADX has remained not just the only federal supermax but also the apogee of a particular strain of the American penal system, wherein abstract dreams of rehabilitation have been entirely superseded by the architecture of control. Throughout our country’s history, there have been different ideas about what to do with the “worst of the worst” of our criminal offenders, ranging from the 19th-century chain gangs, who toiled in enforced silence, to the physical isolation of Alcatraz Island. The use of solitary confinement in the United States emerged as a substitute to corporal punishments popular at the end of the 18th century. The practice was first promoted in 1787, by a group of reformers called the Philadelphia Society for Alleviating the Miseries of Public Prisons. At a salon hosted by Benjamin Franklin, a pamphlet was read calling for the construction of a “house of repentance,” in which solitude could work to soothe the minds of criminals — an enlightened alternative, the group believed, to inhumane “public punishments” like “the gallows, the pillory, the stocks, the whipping post, and the wheelbarrow.” Inmates at Philadelphia’s Eastern State Penitentiary, which opened in 1829, were completely isolated from one another in cells outfitted with skylights, toilets and access to private outdoor exercise yards, where they worked at various trades, took all meals and read the Bible. Other states tried, but quickly abandoned, the so-called Pennsylvania System, and an 1890 Supreme Court ruling against the use of solitary on Colorado’s death row noted that “a considerable number of the prisoners fell, after even a short confinement, into a semifatuous condition, from which it was next to impossible to arouse them, and others became violently insane; others still, committed suicide, while those who stood the ordeal better were not generally reformed.”

The concept soon fell out of favor, and beginning in the 1930s, the hardest cases in the federal system — men like Al Capone and George (Machine Gun Kelly) Barnes — were housed in the converted military prison on Alcatraz Island, until it was closed in 1963 because of the costly upkeep inherent to an island prison. By the end of the decade, many of its prisoners had been transferred to the new “control units” at a federal penitentiary in Marion, Ill., where they were kept in solitary confinement. In 1983, after the assassination of two guards in separate attacks on the same day, by members of the Aryan Brotherhood, the Marion penitentiary was converted to the first modern all-lockdown facility, the entire prison now a solitary unit. (One of the guards’ killers, Tommy Silverstein, is now at the ADX. He has been in solitary confinement for the past 22 years.)

Beginning in 1989 with California’s Pelican Bay, states began building their own lockdown penitentiaries, inspired by the Marion model. The renewed use of solitary coincided with the era of mass incarceration and the widespread closing of state-run mental-health facilities. The supermax became the most expedient method of controlling an increasingly overcrowded and psychologically volatile prison population. A result of this unfortunate confluence has been a network of ever more austere and utilitarian penitentiaries, built specifically to seal off a significant portion of state and federal inmates, using methods that would shock many Americans. According to a 2014 Amnesty International report, more than 40 states now operate supermax prisons. On any given day, there are 80,000 U.S. prisoners in solitary confinement.

Norman Carlson, the B.O.P. director at the time of the Marion attacks, spearheaded the construction of a federal supermax that could eventually replace Marion. Florence, a faded Colorado mining town, lobbied hard for the $60 million prison to be built within its city limits, with residents eventually donating 600 acres of land to the B.O.P.