The answer is today it is only interpreted to include all people while originally it referred only to white men
In 1887, Congress established a commission to regulate the railroads by passing "The Interstate Commerce Act", which was mainly intended to keep railroad companies from becoming monopolies.
Child labor is a continuous thing related to slavery by factories not having enough employees or very poor families not being able to gain enough money would be manipulated by someone promising money and edu. for their child or selling the child into labor or forcing them into it.