City of Chicago’s zoning is rather complex and There’s like a 130 something zoning codes in the villages immediately surrounding the city of Chicago. Plus all the bizarre downzoning in Chicago has made some neighborhoods where apartments stand, noncomforming as they are now zoned single family residential.
Just to throw out a random zoning code. Here’s the lot size and setbacks for unincorporated Cook County and unincorporated Chicago...which those R5 lots are smaller than what the ordinance allows as they were platted out like city lots and never annexed
https://www.cookcountyil.gov/file/12...token=hpgGhAn8
Here’s a map with all the villages and the City zoning codes overlay, plus the municipal boundaries
https://maps.cookcountyil.gov/cookviewer/mapViewer.html