New York Maximum Security Penitentiary is a prison built around a former major American city. The actual prison is a 50-foot containment wall built around Manhattan island.
During a major war with a coalition of the Soviet Union and China, the United States gradually devolved into an authoritarian police state after crime rates soared to unprecedented highs. As a result, the USPF was established as a federal law enforcement agency.
The city of New York, once synonymous with the country, was turned into this prison. It is possible that the city had already been destroyed by then, and the government decided to use it as a prison thereafter. Government forces do not enter the city itself, instead patrolling the wall that encloses it, executing escapees. Over time, the city has decayed. Criminals rule over the fading streets, and all manner of crime, as well as a general state of utter lawlessness, are the status quo of life in the prison. The streets are saturated in car wrecks, litter, furniture, and other debris. Some of the city retains electricity from improvised generators built by the inhabitants.
Snake Plissken is deployed there to rescue the president after his plane is hijacked by insurgents.