From Grand Theft Auto IV
Liberty City was first introduced to the GTA series in the original Grand Theft Auto (2D version). The second appearance it made was in GTA III, where it was divided into three islands. It was the first 3D city in the GTA series and the first in the GTA3D -trilogy. As Rockstar was still working hard on the actual gameplay elements aswell as the engine, the realism of the city didn't get as much attention as they would have wanted from a city like New York. System limitations of consoles had their share of impact of what was even possible to do back then, but with the new generation consoles Rockstar decided it was time to go back to Liberty City for a third time, but make it resemble the real city to a very high detail.
The city is divided into 4 boroughs and New Jersey. They decided to leave out the 5th borough (Staten Island) from New York away from Liberty City simply because they considered it not to be worthwhile addition due to dullness. Liberty City will be smaller than San Andreas in square miles, but it is a lot more dense and larger than any city featured in the GTA series before.
Bohan - The Bronx
Bohan is the Liberty City version of The Bronx in New York. It is also where people go to see sports games, such as the Liberty City Chargers, their football, basketball, and baseball team.
Broker - Brooklyn
Broker is the GTA IV version of Brooklyn. Large amount of detail has been recreated to make it resemble the real deal.
A company called Cher Kov resides in building which is presumed to be the taxi company owned by Niko Bellic's cousing Roman. Niko gets involved into Roman's business as he is in debt and the Russian mafia is coming after him.
Beneath the Offramp of the Alqonquin Bridge Overpass (BOABO)
BOABO (Beneath the Offramp of the Alqonquin Bridge Overpass) is in an industrial area in Broker. It is the recreation of a similar area in Brooklyn called DUMBO (Down Under the Manhattan Bridge Overpass). There is a sugar factory called Twitchins situated there which is the GTA version of the Domino's Sugar Factory situated in Brooklyn.
Little is known about this area of Liberty City except that it is run by a gangster named Vlad.
Algonquin - Manhattan
Manhattan is name Algonquin in GTA IV. The skyscrapers of the borough have been for a big part recreated into Liberty City. The skyline represents that of New York city to a very large extent.
Star Junction is the GTA IV version of Times Square. From the screenshots we have seen of Star Junction it appears to resemble Times Square a lot.
Dukes - Queens
A place where you will probaly have to take your dates to because it has the finest restarants in Liberty City.
Alderney - New Jersey
alderney is unlocked after the mission three leaf clover