Final answer:
The Pure Food and Drug Act of 1906 required drug preparations containing morphine to be properly labeled to indicate its presence.
Step-by-step explanation:
The act that required drug preparations containing morphine to have a label indicating its presence was the Pure Food and Drug Act of 1906. This early piece of consumer protection legislation was enacted to impose federal standards of inspection and sanitation on meatpackers and to require drug makers to list ingredients. The act was inspired by muckraking exposés about adulterated foods and dangerous patent medicines, highlighting the previously unregulated and often unsafe practices that prevailed in the food and drug industries at the time.