FCI Marion in southern Illinois has one of the more historically significant stories in the federal system. It opened in 1963 as United States Penitentiary Marion, built specifically to take on the highest-security inmates after Alcatraz closed that same year. In 1972 it became the birthplace of the "control unit" concept, and after two officers were killed by inmates in October 1983, the entire penitentiary was placed on lockdown, with prisoners held in single cells for roughly 23 hours a day. That lockdown lasted for over two decades and made Marion the model the Bureau of Prisons later used to design the supermax facility at ADX Florence, Colorado. Marion's most restrictive chapter effectively ended in 2007, when the institution was reclassified from a maximum-security penitentiary down to medium security, and it has operated under that designation since, now also including a satellite camp. Families of inmates there today are dealing with a very different facility than the one that made headlines decades ago, but Marion's name is still closely tied to the origins of long-term solitary confinement practices in the federal system, which is worth understanding as background even though current conditions reflect its medium-security status.