Not terrorism, just Chicago's annual November fireworks display

I headed downtown for the usual weekend Fox and Obel trip with a couple friends this evening, and, much to our surprise, all of Michigan Avenue, right below Wacker and further north on Michigan, was packed with families, all just sort of generally congregated, we had no clue why. There didn't appear to be a parade, and there were far too many people for them to have just been stragglers hanging around after an earlier parade. Our bus had been a bit rerouted, not going as far north as usual, which ought to have tipped us off that something was up, but, absentminded U of C students all, we didn't worry about it too much.

Cops were directing people to turn away from Michigan, by the Chicago River, so we started obediently walking east by the river, when suddenly we heard these horrible, loud, explosion-like sounds coming from very nearby. Crowds, a major American city, and loud explosions--bad news, I thought, so I covered my ears with my hands and started walking quickly, at times running. Then I looked over to the river and saw that, from some kind of platform in the water, a whole bunch of fireworks were being set off. Why fireworks, on November 20, and why so scarily close to where people walk around? (Clearly this is my punishment for reading the NYT and not the Chicago Tribune--if I read the local paper, then I might have known more what we'd be in for this evening.)

Turns out many Chicagoans view these loud fireworks in the middle of November as a positive, uplifting event, one worthy of staying out late for with dogs and small children, and are apparently not all convinced, as I was, that any loud, unexpected explosions in the middle of crowds in the middle of a city are to be avoided.