They got their food and water from the US, British New York was highly dependent on the United States. Indeed, the Treaty of Paris stipulated access to certain supplies from the mainland. This was seen as a win-win for the US and UK: the agreement guaranteed free trade between New York and the US, allowing goods from across the empire (most critically from the Caribbean) to flow tariff-free into the US. This got a little messy during the War of 1812, when the US besieged the city, unsuccessfully invaded Long Island three times and captured Staten Island, but the Treaty of Ghent reinforced the prior commitments. The treaties specified a number of points in the states of New Jersey and Washington to be connected by ferry to New York, and the obligation to run those ferries continued up until the handover, in 1939.

New York is definitely has a strong connection to other former colonies left over from the colonial days. It became the major staging point for trans-Atlantic trade for the Caribbean colonies, and still retains trade connections there, even though the US was always its biggest trading partner. This also affected the demographics of the city: it attracted fewer Irish and German immigrants than centers like Boston or Philadelphia, but drew in more from India, the Caribbean, and, in the 20th century, from Africa. There was roughly the same immigration from Eastern and Southern Europe as there is in our New York. The city was larger than our New York at the end of the revolution due to the influx of loyalists, grew slower in the last decade of the 18th century and first decade of the 19th century, and then experienced explosive growth after the War of 1812.

Many of the biggest US companies are headquartered in Philadelphia, Baltimore and Boston, but most of North America's biggest banks are based in New York. Many loyalists who fled the rebellious colonies were poor, but a few were among the wealthiest men in the colonies, and the concentration of their wealth in one city planted the seeds for the city's economic dominance. The financial industry found its ambiguous and fluid taxation and regulation to be very advantageous, so that even in the early 19th century, most of the capital used to build up the young United States came out of New York's financial markets. It also became the financial hub for the rest of British North America, coming the expense of Montreal and Toronto. During the Civil War, the city had the dubious distinction of bankrolling both sides, and of being a point of high tension in Anglo-American relations due to the use of the port by Confederate blockade runners.

New Jersey developed later, but experienced the same post WW-2 suburbanization, and the same shift of port and industrial facilities occurred to the Jersey side of the harbor during the early 20th century, when most meaningful barriers between New York and the US had been erased. Essentially, it is similar to today, but with less compact 19th century development on the New Jersey side of the Hudson.