Eric Walker added Inside America’s Toughest Federal Prison - The New York Times to a number of topics

Eric Walker added United States Penitentiary, Marion - Wikipedia to 1963 USP Marion

Eric Walker added 1995 ADX Florence and 1963 USP Marion and Entombed: Isolation in the US Federal Prison System and Supermax prison - Wikipedia to Supermax prisons in the United States, and added Supermax prisons in the United States to Detention and imprisonment in the United States and Supermax prison

Eric Walker added Inside America’s Toughest Federal Prison - The New York Times and United States Penitentiary, Marion - Wikipedia to USP Marion, and added USP Marion to Supermax prisons in the United States and Lockdown penitentiaries

Eric Walker added 1989 Pelican Bay State Prison and 1963 USP Marion to Lockdown penitentiaries, and added Lockdown penitentiaries to Detention and imprisonment