By 1880, the United States had become the world's leading producer of goods due to an unlimited labor force from immigration, abundant coal supplies, iron mining, and the discovery of oil. New technologies like the telephone, light bulb, electric power, and Bessemer steel process drove innovation, while railroads connected markets and fueled industrial growth. Major industrialists like Rockefeller, Carnegie, and Morgan built vast fortunes in oil, steel, and finance. The railroad industry grew rapidly but also faced scandals and calls for regulation of rates and practices.