Much of what had led to Chicago’s increased crime rates during this period was largely caused by the start of prohibition in 1920. This ban had inadvertently birthed a network of organized crime across the city, which had thrived on the illegal production and sale of alcohol. As gangs grew to power, their agendas began to clash: disputes over territory and underground breweries became a common conflict, and ultimately, the easiest solution to these problems was achieved through violence. But beyond prohibition, 1920 also marked another key event: the arrival of mobster Al Capone in the city of Chicago. 

During his first few years in Chicago, Al Capone worked for his boss and friend, Johnny Torrio, in the city's most notorious gang: the Chicago Outfit. After nearly being killed in 1925, however, Torrio decided to retire, handing full authority and control down to Capone. Unlike Torrio, Capone was infamous for his reckless and flaunting behavior. Thus, with his rise to power, gang-related shootouts and bombings had become an even more common problem throughout Chicago's streets.

Of all the violence that the city saw under Capone's reign, however, nothing shocked the public as much as the Saint Valentine’s Day Massacre in 1929. On February 14th, Capone’s henchmen, disguised as police, had lined up and killed seven members of the opposing Moran gang. The pure brutality of this crime, as well as how easily the men responsible were able to commit it, stirred public outcry on an international scale, and ultimately called on Chicago to answer for its ineptitude in fighting crime.  

Sources:

“Al Capone.” History.com, A&E Television Networks, 2009. www.history.com/topics/al-capone.

"Al Capone." Wikipedia. Wikimedia Foundation. Web.

“Prohibition.” History.com, A&E Television Networks, 2009, www.history.com/topics/prohibition.

“Prohibition in the United States.” Wikipedia, Wikimedia Foundation. Web.