A police shootout in Chicago, 1930
The Beer Wars were a series of Prohibition-era gang wars which occurred on the streets of Chicago from 1920 to 1933 as rival gangs, such as Johnny Torrio and Al Capone's Chicago Outfit, Bugs Moran's North Side Gang, and Joseph Saltis' organization, fought for control of the city's lucrative black markets. Organized crime experienced a major boost after the United States government outlawed the sale and manufacture of alcohol in the Eighteenth Amendment to the US Constitution, ratified on 16 January 1919 and beginning on 17 January 1920; as local business owners established "stills" to produce alcohol and "speakeasies" to serve as underground drinking establishments, criminal outfits muscled in on local business owners and engaged in widespread racketeering, often aided by corrupt local politicians. Crime in Chicago tripled during the 1920s as gang engaged in drive-by shootings against rival gang members (often with the new Thompson submachine gun, invented for use by the US Army in World War I), bombed businesses which refused to pay for criminal "protection", and gangs battled for control of smuggling routes and territories. These gangs not only engaged in "bootlegging", but also engaged in illegal prostitution, gambling, and theft. Law enforcement often discriminated against African-Americans, white ethnics, and immigrants with their Prohibition laws, and Prohibition came to be deeply unpopular among racial and ethnic minorities in the United States. In Chicago, the Democratic mayor William Emmett Dever reluctantly upheld Prohibition and ordered crackdowns on organized crime in the city, leading to Chicago being touted as the "driest" city in the country by the end of his first year in office, 1923. However, an all-out gang war erupted on the city's streets in 1925 as the Italian-dominated Chicago Outfit engaged in a bloody turf war with the Irish, Polish, Jewish, and German-majority North Side Gang. The most famous incident of the "Beer Wars" occurred on 14 February 1929 in the "Saint Valentine's Day massacre", during which four assailants dressed as Chicago Police Department officers executed seven members of the North Side Gang in a Lincoln Park garage with "Tommy guns". That same year, the Republican politician William Hale Thompson was elected Mayor of Chicago after promising to end the enforcement of Prohibition in the city; his campaign was supported by Al Capone, whose mafiosi later grenaded polling stations in the "Pineapple Primary" to support candidates loyal to Thompson in 1928. Thompson and several ward bosses were in the pockets of Capone, who reigned over the city with impunity until 17 October 1931, when the efforts of Treasury Agent Eliot Ness and his team, "The Untouchables", resulted in a tax evasion conviction and an 11-year prison sentence for Capone, "Public Enemy No. 1". Prohibition was ultimately repealed by the Twenty-First Amendment on 5 December 1933, forcing the city's remaining gangs to move into new rackets. Chicago continued to experience violent crime over the next few decades, as urban decay and the rise of "white ethnic" and Black gangs led to continued gang warfare, and crime rates would see another sharp rise from the late 1960s to 1996 and again after 2016.