1. What was the primary legal issue in Hammer v. Dagenhart?
2. What was the Supreme Court's holding in Hammer v. Dagenhart?
3. Who was the plaintiff in Hammer v. Dagenhart?
4. What did the Keating-Owen Child Labor Act of 1916 aim to achieve?
5. What was a significant result of the Supreme Court's decision in Hammer v. Dagenhart?