Final answer:
Large smuggling operations during Prohibition resulted in alcohol being illegally shipped into the United States notably from Canada, particularly through border cities like Detroit.
Step-by-step explanation:
During Prohibition, large smuggling operations developed, and distributors began illegally shipping alcohol from various locations. The question asks from which of the provided options alcohol was smuggled into the United States. The correct answer is Canada. Prohibition law enforcement was overwhelmed, leading to rampant illegal activities such as bootlegging, and the rise of organized crime.
Canadian and Mexican borders saw significant smuggling activities, as these countries did not have similar Prohibition laws, making them major production centers for alcohol. Cities like Detroit, which bordered Canada, saw a substantial amount of alcohol smuggled from Canadian sources, such as the Detroit River, controlled by gangs like the Purple Gang and supplied to notable figures such as Al Capone.