It was on this day in 1837 when the Windy City was incorporated.
Mayor Brandon Johnson is celebrating with cake at the Lookingglass Theater Company.
Chicago's Poet Laureate, Mayda Alexandra del Valle, will also read a poem.
Wednesday's celebration is from 10-11 a.m.
The first 189 people will receive complimentary treats.
Stan's Donuts, Fannie May collaborate for Chicago birthday donut
Also for Chicago's birthday Stan's Donuts & Coffee and Fannie May teamed up to create a limited-edition donut inspired by Fannie May's classic Trinidad chocolate.
The donut is a chocolate yeast Bismark, filled with rich chocolate cream and dipped in toasted coconut white chocolate.
The donut is available through March 10.