[4] USP Marion was built and opened in 1963 to replace the maximum security federal prison on Alcatraz Island in San Francisco, which closed the same year.

On May 24, 1978, Trapnell's friend, 43-year-old Barbara Ann Oswald, hijacked a St. Louis based charter helicopter and ordered the pilot, Allen Barklage, to fly to USP Marion.

Barklage complied, but he wrestled the gun away from Oswald and fatally shot her while he was landing in the prison yard, thwarting the escape.

[10][11] On October 22, 1983, correctional officers Clutts and Hoffmann were killed in separate incidents only hours apart, both at the hands of members of the Aryan Brotherhood, a white-supremacist prison gang.

[14] As a result of the murders of Clutts and Hoffmann, USP Marion went into "permanent lockdown" with all inmates locked in their cells for the majority of the day.

[15] USP Marion was effectively transformed into a "control unit" prison, also called supermax, or "super-maximum" security.

This method of prison operation involves the keeping of inmates in solitary confinement for 23 hours a day, and does not allow communal dining, exercising, or religious services.

Years later, Norman Carlson, director of the Bureau of Prisons at the time of the Marion incident, said that as draconian as the permanent lockdown was, he believed it the only way to deal with "a very small subset of the inmate population who show absolutely no concern for human life."

The "control unit" model at Marion was later the basis for ADX Florence, which opened in 1994 as a specifically designed supermax prison.

"By concentrating resources in this fashion, it will greatly enhance the agency's capabilities for language translation, content analysis and intelligence sharing," according to the Bureau's summary of the CMU.