Final answer:
Four cities that have been the second-largest by population in the U.S. after New York City are Philadelphia, Chicago, Los Angeles, and St. Louis.
Step-by-step explanation:
In the context of U.S. urban development, New York City has been the leader since the first census in 1790. Four cities have intermittently held the position of being the second-largest by population in the United States. These cities are Philadelphia, Chicago, Los Angeles, and for a brief period, according to historical data, St. Louis also climbed to this rank around the turn of the 20th century. New York City maintained its lead due to its transportational advantages, such as the port on the Atlantic Ocean, the Hudson River, and the opening of the Erie Canal.
Specifically, during the time span from the end of the Civil War to World War I, we witness tremendous growth in these urban centers. Chicago, branded the "Second City", saw its population soar to the two-million mark, establishing it firmly as New York's closest rival in terms of urban population size. Meanwhile, Philadelphia nearly tripled its population, and Los Angeles eventually grew to anchor a Combined Statistical Area (CSA) with a population exceeding 18 million.