hen Lewis Hine began to make photographs for the National Child Labor Committee, the employment of small children in mines, factories, and fields was common. While some states had passed child labor laws, generally they were weak, and enforcement was haphazard. In 1911 some two million children under sixteen years of age were a regular part of the American workforce. Many of them worked twelve hours a day or more.

Thanks in large part to the political campaign waged by the NCLC, a campaign starkly illustrated by Hine's powerful photographs, Americans came to believe that the federal government should set limits on child labor. Congress passed laws in 1916 and 1918, but the Supreme Court declared them unconstitutional because they infringed on states' rights and "denied children the freedom to contract work." In 1924, Congress passed a constitutional amendment authorizing a national child-labor law, but active lobbying prevented a sufficient number of states from ratifying the amendment.

Child labor began to disappear only during the Great Depression of the 1930s, in no small part because adults found themselves competing for the lowest-paying positions, those held by children. Federal regulation of child labor finally came about in 1938, when President Franklin D. Roosevelt signed the Fair Labor Standards Act, which set minimum wages and maximum hours for all workers employed in interstate commerce, and also placed limitations on child labor. Children under sixteen were prohibited from working in such dangerous occupations as manufacturing and mining.

The Supreme Court upheld these laws, which Congress expanded in 1949 to cover commercial agriculture, transportation, communications, and public utilities. In other occupations, federal laws prohibited children under sixteen from working during school hours, and limited the number of hours they could work after school and on weekends.