Is there any possible way to geographically expand NYC ? How do you add new counties to the city and is there anyway to include New Jersey counties ? How would a multi-state city work ?
Well, this is a Before 1900 thread, so couldn't you potentially alter the position of the state boundaries?
Within the framework of the American Federal system, there's no way for New York City to incorporate parts of New Jersey without either New York or New Jersey ceding the territory, or some sort of constitutional exception.
Why? Cities aren't mentioned in the constitution, cities aren't required to be in a single state. The examples of Lloydminster and Alsask on the Alberta/Saskatchewan border show that it's possible to have cities that span subnational boundaries.
There are a few instances of cities straddling state lines, but they're really sister cities with the same name. Texarkana comes to mind immediately. There's also one on the Nevada/Utah border but I can't remember the name right now.
Why? Cities aren't mentioned in the constitution, cities aren't required to be in a single state. The examples of Lloydminster and Alsask on the Alberta/Saskatchewan border show that it's possible to have cities that span subnational boundaries.
I was hoping there would be a way to have a multi-state NYC though. It can expand up and east towards Long Island. But is there any plausible way for New Jersey counties to be with NYC ?
A multistate unitary municipal authority isn't possible under the current Federal system. You'd have to change the constitution.
Or, have New York DCity declared a separate state, with some sort of convention between states discussing what communities would then choose to belong to it and which would remain in their original states.
You could have NYC expand through land reclamation; that's largely what Boston did in OTL.
New York did quite a bit of that too IOTL, plus most of Boston's expansion was actually annexing surrounding towns like Dorchester and Roxbury.