On March 4, 1837, Chicago was officially incorporated as a city. A lot has changed in the 179 years since then (buildings, roads, a great cocktail scene—just to name a few), and it's worth remembering the rich history that made the city what it is today.
Today, you can celebrate the city's birthday at the Chicago History Museum, where they'll be serving up Eli's Cheesecake and lemonade (which is probably not the cuisine enjoyed by the city's earliest settlers) to commemorate the brave souls who saw a nasty stretch of swamp next to Lake Michigan and thought, "We should totally build a giant city here." The event will include music, and anyone who shares a birthday with the city will get a "special certificate."
The celebration runs from 11am to 1pm. If you can't make it, there are plenty of other ways to honor the city's history such as placing a lantern near a cow, herding some cattle up Milwaukee Avenue or building a murder castle.