The population increased threefold because of immigrants. There were both positive and negative reasons to move to America. The negative reasons included: poverty of displaced farm workers, overcrowding and joblessness in European cities as a result of a population boom, and religious persecution. Positive reasons to emigrate included: political and religious freedom, economic opportunities, and the abundance of industrial jobs. The new wave of immigrants frightened Americans because of their customs, different faiths, poverty, and illiteracy. Laws restricting immigration began with the Chinese Exclusion Act of 1882. Then came a restriction on "undesirables", people who have ever been convicted of criminal acts or diagnosed as mentally impaired. Restrictions were supported by labor unions (feared that they would lose their jobs to immigrants), the American Protective Association (a nativist society that was prejudiced against Roman Catholics), and Social Darwinists (viewed the new immigrants as inferior to English and German stocks). But none of these restrictions really stopped the wave of newcomers. At the turn of the century, almost 15% of the U.S. population were immigrants.
Urbanization and industrialization developed together. The number of improvements in urban transportation played a role in the growth of the cities. Cities provided a central supply of labor for factories and also a principal market for factory-made goods. Mass transportation included electric trolleys, subways, and suspension bridges, such as the Brooklyn Bridge. It segregated workers by income, allowing the wealthy to move into the suburbs. American cities could not deal effectively with the build of waste, pollution, disease and crime, so upper and middle classes move to the suburbs to escape. Factors that promoted suburban growth included: abundant land available at low cost, inexpensive transportation by rail, low-cost construction methods like wooden houses, ethic and racial prejudice, and Americans wanting privacy. There were ethic neighborhoods where immigrants could maintain their culture and language.