Liberty Island is based upon real life Manhattan, consisting of a high-rise downtown in the south area, a high-rise Midtown in the north. Liberty Island has six neighborhoods, including the two smaller islands. It was founded in 1603[1]
↑ 1.01.1"... Founded on land bought off native Indians for just $37, a barrel of mead and a sack of feathers by Belgian settlers in 1603, the ancient 5 boroughs of Liberty Island (incorporating Nixon Island and Law Island), The Brix, Estoria, Kings and Brocklyn have effectively been joined in the metropolitan area by urban areas from the neighbouring state of New Guernsey... " - Official GTA website -> Cities -> Liberty City
↑Liberty City's description on the official GTA website.