Los Angeles Island is a former major city of the United States. After a severe earthquake that destroyed much of the city and caused floods rendering it isolated from the mainland, the government began using it as a prison for criminals and undesirables, much like New York City. Compared to the New York city-prison, the Los Angeles one is in a much worse state. Infrastructure is mostly in tatters due to the earthquake and subsequent flooding. While New York City was certainly extremely dangerous, the Los Angeles prison is implied to be much more violent and unpredictable.
Much like the previous city-prison, the area has devolved into lawlessness, being run by criminals and gang members, and housing criminals from the most petty to the most violent.