I often wonder why since there is Five boroughs, why each Family weren't given one area of operation? Even if they chopped up Manahattan and it was neutral (because of Legitimate business), there is enough surrounding area to work out that 5th territory..... especially in those days
Territory was determined by who got to a place first and this was influenced by chain migration.
For example, the Gambino and Colombo families trace their roots back to immigrants from, predominantly, Palermo and Villabate, which explains their proximity and overlap in territories in Brooklyn. Mafiosi originally settled mostly in Manhattan, Brooklyn, and the Bronx, but demographic changes brought about movement to Queens, Staten Island, and areas outside of NYC.
By the 1920s, all five families were already established, so to reorganise them in such a way as to relegate one family per borough would have been a disaster.
