Beer drinkers can thank Chicago's extremely cold winters and warm humid summers for helping to create the much sought-after Bourbon County Barrel Stout taste. The brewery keeps the barrel-aging room under a limited climate control, looking to take advantage of the extreme swings in temperature.
"We want the bourbon and oak character to pull from the wood, and the expansion and contraction that happens through temperature and humidity changes during the seasons is really something," Siegel said. "It's a Chicago thing. We get more extreme cold to hot weather than just about any other place."
Read MoreThanksgiving meal for only $35K
The seasonal aging process is also part of what makes the brewing process more complex. The need to cover different seasons means the beer must spend a minimum of eight months and typically as long as 12 months aging in the barrel.
For the Bourbon County series, this involves more than 3,000 whiskey barrels. The Goose Island sour beer program includes another 2,500 wine barrels used to age those beers.
Currently there is no high-tech system for tracking the thousands of barrels in use, as they are monitored the old fashioned way: with notes taken on index cards stapled to the barrels.
"We've got some index cards on the wine barrels that every single square centimeter has writing on them, going back to three, four, five years. You can see exactly the kind of the life of this barrel, at least the life it's lived at Goose Island. It's just sort of a paper card history," Siegel said.