Final answer:
Manhattan, Brooklyn, and the Bronx are all boroughs located within New York City, the largest and one of the most influential cities in the United States.
Step-by-step explanation:
You would find Manhattan, Brooklyn, and the Bronx in New York City. This city is not only the largest city in the United States but also an epicenter of economic and cultural activity. It outgrew other East Coast cities because of its strategic advantages in transportation, such as the port on the Atlantic Ocean, the navigable Hudson River, and the Erie Canal.
These helped establish its prominence in trade and population growth as evidenced by historical population numbers. The megalopolis, extending from Washington, D.C. to Boston, includes New York City as its anchor and is central to both the U.S. and Canadian economies.