After the Civil War, the United States underwent a Second Industrial Revolution. American ingenuity and entrepreural spirit led men like Thomas Edison, Andrew Carnigie, and John D. Rockefeller to establish big business and amass huge fortunes. Immigration continued to rise as new immigrants from southern Europe arrived in America to work in the expanding cities. Working conditions forced many laborers to form unions for better working conditions and higher wages. It was the beginning of the Industrial Age and America was its leader.