Manhattan Island in New York City is the natural transport hub of the United States. It is the terminus of the Hudson River, which via the Erie Canal accesses the Great Lakes. It also sits a short distance from the northern extreme of the Intracoastal Waterway, connecting New York to the mouth of the Mississippi. From New York City, nearly any part of the eastern half of the country can be reached with ease.
New York’s centrality also makes it the natural location for a financial hub. Trade on rivers naturally concentrates at maritime intersections such as Manhattan. The revenue from such concentrations requires banks, and it should come as no shock that New York City has the densest concentration of financial activity in the United States.
For more on how rivers shape economies in general, and how American rivers shape the United States in specific, see Chapter 4 of
The Accidental Superpower.