Harvard professor Lisa McGirr has a fine new book on Prohibition, The War on Alcohol. She argues persuasively to me that, rather than being a foolish experiment sandwiched between World War I and the New Deal, it had a profound impact on the size and focus of government in America, and for the worst.
The 18th amendment was enacted under pressure from a strange coalition of the Women's Christian Temperance Union, the Ku Klux Klan, big business leaders like John D. Rockefeller and Henry Ford, and Protestant ministers. The need for grain for troops made it easy for Woodrow Wilson to restrict alcohol production and consumption at the start of American involvement in the first world war.
McGirr notes that the second decade of the 20th century saw adoption of several amendments to the Constitution, the first since the Civil War: direct election of Senators, income tax, prohibition, and female suffrage. Legalization of the income tax made banning liquor easier because as late at 1910, the liquor tax amounted to a full 30% of federal revenues.
The pernicious effects of the 18th amendment were numerous. Government expanded to regulate and enforce the Volstead Act. Prison populations ballooned. Politicians outbid each other with laws for draconian punishments of liquor violations. A double standard quickly evolved, poor whites and blacks were prosecuted; the rich went to their speakeasies. Federal law enforcement became more intrusive with techniques like the first wiretaps and when states refused to join the fight. [Gov. Al Smith got New York to repeal its state laws on prohibition in 1923.]
Organized crime expanded to service the violators, and federal and local police efforts were undercut by corruption. As people shifted from alcohol to other drugs, the politicians followed with harsh laws against other substances. As late as 1925, President Coolidge had said that "religion [is] the only remedy" against lawlessness. But he and successor Herbert Hoover enlarged the police state to fight the crimes linked to drugs and alcohol.
I don't know what if any lessons we might draw to deal with drug laws today -- though it is sad that the places in America with the most restrictive laws on alcohol today are also the places with the greatest amount of meth use.