According to Homberger (p.55), when the British Army and their loyalist allies evacuated New York in 1783, the population of the city was 12,000. The demobilization of the revolutionary army, and the return of many patriots who had fled the city when the occupation began, caused the population to more than double between 1783 and 1786. Nonetheless, Philadelphia remained the new republic’s largest city, and was not to lose its place for two decades. When the first federal census was completed in 1790 Philadelphia, with a population of 42,520, substantially exceeded New York City at 33,131. Rapid population growth over the next three decades largely explains the dramatic physical expansion of the city. As we could see New York’s population outstripped “natural” growth, and was enhanced by a flood of migrants into the city from New England. Needless to say that population during any way is getting down. But what factors effect on the population growth after the war is really important. For New York these reasons are the following: NY is a commercial center, it is near water so people could fish for food, entry to the ocean, port and transportation. There are a lot of American people died during the revolutionary war, but people came back there, came new people and will come then.