The 18th Amendment, prohibiting the sale of intoxicating liquors in the United States, was ratified by the Michigan legislature. Michigan, which went dry on May 1, 1918—over a year before the 18th Amendment providing for national prohibition became effective—proved to be a battleground for the smuggling of illegal booze into the United Sates. It was estimated that during the years of Prohibition (until 1933), 75 percent of all the booze smuggled into the United States crossed at the Detroit/Windsor border.