That meant they were immigrants or the children of immigrants, overwhelmingly from either Irish or German-speaking families. Descendants of German immigrants, who arrived in great numbers just as the Midwest was opening for settlement in the mid-nineteenth century, still make up the majority ethnicity of a wide swath of middle America.

population historians discovered that the most mobile city-dwellers were often wage-workers and the poor. People who owned businesses and valuable real estate were much more “persistent,” in demographic terms, because they were in a sense anchored by their possessions. Over time, though, the greater persistence of more prosperous residents often allowed them to gain greater political power than poorer people who in many cases did not stick around long enough to organize; or often even to vote

Much of the U.S. population growth of the first half of the nineteenth century was due to the extremely high birth rates of the generations just before and after the American Revolution, when the average family had well over four children and the population actually doubled every generation. After the War of 1812, many more were immigrants from foreign countries. Some of the first migrations of large groups followed the Irish Famine in 1845 and a series of failed socialist revolutions in the German states in 1848.

By 1850, Boston had 137,000 residents, New York 515,000, Chicago 30,000, San Francisco 21,000, and Los Angeles 1,600. By 1900, although only forty percent of Americans lived in cities or large towns, Boston had grown to 561,000, New York to 3.4 million, Chicago to 1.7 million, San Francisco to 343,000, and Los Angeles had 102,000.