During the peak of industrialization in America in the decades following the Civil War, which group of Americans did most of the low-paying, back-breaking factory work?

The workplace was changing as machines became common and the demand for unskilled workers brought new groups into the workforce, including immigrants, women, and children. By 1920, nearly 20 percent of all manufacturing workers were women, and 13 percent of all textile workers were younger than 16 years old.