Political cartoon from New York Herald 12/20/1897---"The new instrument Tammany will play on after January 1"
(via How a group of cities combined to form 'Greater New York' - NY Daily News)
It was concern for the port that had led Andrew Haswell Green to first propose consolidation 30 years earlier. Green had saved New York's ruined finances in the 1870s after the fall of the legendarily larcenous Tammany boss William Marcy Tweed; he had been a key player in the creation of Central Park, the Museum of Natural History and the forthcoming New York Public Library; through all these public-spirited years he had argued for an "imperial city," one unified governmental instrument that would, chiefly among other things, centralize the port's administration and insure continued commercial importance.
Notwithstanding the staunch support of New York's mercantile leaders, Green got nowhere at all with the idea until the early 1890s, when, in the legislative corridors of the Albany he controlled utterly and absolutely, Republican State Sen. Thomas Platt looked upon Green's proposal for a supercity and saw that it was good.
The implications were clear to GOP boss Platt: The multitudes of a much larger New York might easily outnumber the Manhattan immigrants who were forever throwing their votes to Tammany's Democrats. Elated by the prospect of an unbroken string of Republican mayors, Platt immediately began oiling the legislative machinery to make Greater New York happen.
Local voters would have to ratify the plan, of course, and they debated it for several years. Manhattan was wildly in favor, and the Bronx was already quite happily being annexed to Manhattan anyway. Long Island City and most other Queens communities were eager to tap into Manhattan's tax base and water supply. Staten Island liked the idea of cheap ferry transportation. In November 1894, the citizens voted yea.
Brooklyn was another story...