In the early 1800s, the US was relatively new (25 years old), and so had not developed into an industrial economy. Cotton farming was widespread during the period as the conditions in the south permitted it, it was vital for the industrial revolution in Europe and was easily grown and cultivated.
So basically Cotton farming is your answer :)
The Eighteenth Amendment declared the production, transport, and sale of intoxicating liquors illegal, though it did not outlaw the actual consumption of alcohol. Shortly after the amendment was ratified, Congress passed the Volstead Act to provide for the federal enforcement of Prohibition. Perhaps the most troubling effect anti-alcohol laws had in the United States was the growth of organized crime. Though organized criminal gangs had already begun to gain power through prostitution and gambling, the 18th amendment made it possible for those gangs to make even more money.
World Health Organization
