It was still the best UI option despite that - if you entered a ZIP that corresponded to multiple states/counties we'd pop up a second box that asked you which you lived in, but for 99% of people it was all we needed

I'm thinking an opportunity was missed here.

1. They kept the Chicago grid on the edge streets of the village so that, e.g., 110 North Austin would be across the street from 111 North Austin and

2. If they had kept the usual new 100 at each block system, the north-south streets on the south end would have been 1200–1249 which would have been identical to the numbers of the next block south in Berwyn and Cicero so the last block on the north-south streets is instead 1150–1199.

Contrast the borders of Los Angeles which in some areas are almost fractal in their complexity (there are buildings which straddle the boundary between L.A. and its neighbors and many blocks where adjacent buildings are in different cities). For whatever reason, the powers that be decided that the incompatible address numbering between adjacent cities should be retained so you will have weird discontinuities in building numbering along a block depending on what city the building lies in. I remember my wife having a doctor’s appointment in a building which was one of those which crossed the border so it had two different addresses assigned to it, one for Los Angeles and one for Beverly Hills.

A few comments here suggest this isn't true.

If you want to reduce input to one field, the autocomplete based on the street address that I brought up is the best experience I've come across.