There was never a city called "Manhattan". Manhattan has always been just the name of an island (and, I believe, the original tribe that lived there). New York (the city) once only comprised a small part of the island, with various other settlements (Greenwich Village, Harlem, etc.) elsewhere on the island. New York's boundaries kept moving north, gradually absorbing the rest of Manhattan island, and then a portion of Westchester County (which became The Bronx). Then, in 1898, the existing New York City merged with the counties of Queens, Richmond, and Kings. Kings County at the time contained a rather large city, Brooklyn.