Tavern operators turned to breweries, often Milwaukee-based Schlitz, which supplied not only the buildings for these watering holes, but also the necessary supplies and equipment. The concept, which came from England, is called a tied house.
But saloon keepers, in exchange for this largess, were compelled to purchase the brewers' beer; that's the tie, or to use a more modern term, tie-in.
Pictured below is a Schlitz tied house at 94th and Ewing on the Southeast Side. It's believed to be the last Schlitz bar in Chicago with its original stained glass Schlitz globe logo.
Above of course is the Schlitz stained glass. Note the carved stone version above it on the building.
The Voltstead Act of course created a different type of tied house, ones in Chicago often had to buy beer from Al Capone.
Legal beer ,wine, and alcohol sales returned after the most lame-brained and destructive amendment to the US Constitution was repealed in 1933, but alcohol was more regulated than ever. In Illinois, direct sales from breweries, wineries, and distilleries to stores, restaurants, and bars, and well, to anyone, was banned. That law is still in effect. Booze, brew, and wine producers sell their goods to distributors, who then sell it to properly-licensed retailers and food and beverage establishments.
The era of tied houses was over in Illinois and elsewhere, as other states have tough controls on reselling alcohol too.
These distributorships are akin to having a license to print money.
Shortly after the Reverend Jesse Jackson called off an Operation PUSH boycott of Anheuser-Busch, the brewer of Budweiser, two of his sons mysteriously purchased a Chicago distributorship with territorial exclusivity in a large part of the city. They Jackson brothers sold their golden goose in 2013.
There are about three dozen former tied houses in Chicago, most of them ex-Schlitz taverns.