Not a new idea. Here's a call for it from 1905:
"The time is comm' and though I'm no youngster, I may see it, when New York City will break away from the State and become a state itself. It's got to come. The feelin' between this city and the hayseeds that make a livin' by plunderin' it is every bit as bitter as the feelin' between the North and South before the war. And, let me tell you, if there ain't a peaceful separation before long, we may have the horrors of civil war right here in New York State. Why, I know a lot of men in my district who would like nothin' better today than to go out gunnin' for hayseeds!
New York City has got a bigger population than most of the states in the Union. It's got more wealth than any dozen of them. Yet the people here, as I explained before, are nothin' but slaves of the Albany gang. We have stood the slavery a long, long time, but the uprisin' is near at hand. It will be a fight for liberty, just like the American Revolution. We'll get liberty peacefully if we can; by cruel war if we must.
Just think how lovely things would be here if we had a Tammany Governor and Legislature meetin', say in the neighborhood of Fifty-ninth Street, and a Tammany Mayor and Board of Aldermen doin' business in City Hall! How sweet and peaceful everything would go on!
The people wouldn't have to bother about nothin'. Tammany would take care of everything for them in its nice quiet way. You wouldn't hear of any conflicts between the state and city authorities. They would settle everything pleasant and comfortable at Tammany Hall, and every bill introduced in the Legislature by Tammany would be sure to go through. The Republicans wouldn't count.
Imagine how the city would be built up in a short time! At present we can't make a public improvement of any consequence without goin' to Albany for permission, and most of the time we get turned down when we go there. But, with a Tammany Governor and Legislature up at Fifty-ninth Street, how public works would hum here! The Mayor and Aldermen could decide on an improvement, telephone the Capitol, have a bill put through in a jiffy and—there you are. We could have a state constitution, too, which would extend the debt limit so that we could issue a whole lot more bonds. As things are now, all the money spent for docks, for instance, is charged against the city in calculatin' the debt limit, although the Dock Department provides immense revenues. It's the same with some other departments. This humbug would be dropped if Tammany ruled at the Capitol and the City Hall, and the city would have money to burn." -- George Washington Plunkett [1]
[1] http://www.gutenberg.org/files/2810/2810-h/2810-h.htm