American cities changed drastically during the 1920 s because of factors above and beyond those related to the automobile. First, the decade saw millions of people flock to the cities from country farmlands; in particular, African Americans fled the South for northern cities in the post–World War I black migration. Immigrants , especially eastern Europeans, also flooded the cities. As a result of these changes, the number of American city dwellers—those who lived in towns with a population greater than 2 , 500 people—came to outnumber those who lived in rural areas for the first time in . history.