During the late 19th century, the United States underwent rapid industrialization driven by three key factors: abundant natural resources like oil and iron, governmental support of industry, and urbanization. New inventions in electricity, the typewriter, telephone, and steel production transformed the economy. The railroad industry expanded dramatically across the country, standardizing time zones and connecting markets. This period also saw the rise of large corporations, labor unrest over poor working conditions, and the emergence of unions seeking better treatment of workers.