In Grand Theft Auto IV, the neighboring state based on New Jersey is Alderney.
Liberty City is GTA IV’s fictional version of New York City, divided into four borough-like areas: Broker, Dukes, Bohan, and Algonquin. Alderney lies across the water to the west and is treated as a separate neighboring state rather than another Liberty City borough.
Its design draws on New Jersey’s dense urban and industrial character. Alderney City evokes places such as Jersey City and Newark, while the state also includes suburban neighborhoods, highways, factories, and the Alderney State Correctional Facility. This mix distinguishes it from the more concentrated Manhattan-inspired Algonquin.
A common mix-up is choosing one of Liberty City’s named boroughs. Dukes is based on Queens, Bohan on the Bronx, and Algonquin on Manhattan; only Alderney represents the New Jersey-inspired neighboring state. Alderney also appears in GTA IV’s story expansions, The Lost and Damned and The Ballad of Gay Tony.