After the Civil War, the U.S. transformed itself from an agricultural nation based on farming to a major industrial power. By 1900, the U.S. had emerged as the leading global industrial power. To fuel that growth, workers were needed, and business owners turned to children as a source of labor. From 1870 to 1900, during the peak wave of immigration, the number of child laborers in U.S. industry grew from 750,000 to just over 1,750,000. Although American children had always worked, this labor was different. No longer under the supervision of families on farms, industrial child laborers, many of them immigrant children, worked in dangerous factories and mines under the direction of supervisors and factory owners.