In recent decades, life imprisonment without the possibility of parole (LWOP) has developed into a distinctive penal form in the United States, one firmly entrenched in US policy-making, judicial and prosecutorial decision-making, correctional practice, and public discourse. LWOP is now a routine part of contemporary US criminal justice, even engrained in the nation's cultural imaginary, but how it came to be so remains in question. Fifty years ago, imprisoning a person until death was an extraordinary sentence; today, it accounts for an increasing percentage of all US prisoners.