Where did the new residents of America's rapidly growing cities come from?

The availability of land in the nineteenth century was one of the factors that distinguished the U.S. from European nations. Thomas Jefferson had urged that the U.S. remain a nation of small farmers and towns, so as to avoid the crowding and poverty of industrial centers in England and elsewhere in Europe. We often think of Americans migrating Westward in search of farms in the nineteenth century, but they also migrated from the countryside to the cities. Cities gained more new residents as a result of the millions of immigrants who arrived in America between 1880 and 1920. During the World War I, thousands of African-Americans migrated from the South to Northern cities in search of factory jobs, further swelling cities' population and adding to their extraordinary diversity.

At the time of the American Revolution, only five percent of Americans lived in cities of 2,500 or more people. By 1860, that percentage had grown to 20 percent. In 1900, 40 percent of Americans lived in cities. And the 1920 Census revealed that, for the first time in the nation's history, a majority (51 percent) of citizens lived in cities, rather than in small towns and rural areas. America's largest cities grew very rapidly: New York, the nation's largest city, topped 3 million people by 1900, and Chicago exceeded 1 million.