Yesterday, June 4, was the date upon which the first minimum wage law was passed. It happened in Massachusetts in 1912. Read the history here. It didn't cover all workers, only women and children. Sadly, the women and children of that time were taken advantage of by the owners of mills and other businesses.
If you don't believe me, take a look at the captions of some of the photos taken by Lewis Hine, which are available online in the National Child Labor Committee Collection at the Library of Congress.
We have several books on child labor history, which are illustrated with astonishing photographs of children. Look for Susan Campbell Bartoletti's Kids on Strike! [J 331.892 BAR], Growing Up in Coal Country [J 331.3 BAR], or, Russell Freedman's Kids at Work: Lewis Hine and the Crusade against Child Labor [J 331.3 FRE]