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. Despite this, Los Angeles Island is seen by many as the only free zone left in the world as many of the people on the island have way more freedoms than they had in the theocratic police state the United States had evolved into.
Unlike New York, many of the residents of Los Angeles Island are armed to the teeth with various kinds of firearms ranging from handguns, submachine guns, rifles, shotguns, machine guns, grenade launchers and anti-tank missiles.
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. In addition to these gangs, Los Angeles Island is also filled with "moral criminals" i.e. American citizens who fell afoul of the President's Moral America laws and were deported to the island under Directive 17.