So you learned the Chicago Catholic Church Records from 1833 – 1925 are online at Family Search https://www.familysearch.org/search/collection/1452409. Some of the collection has been indexed but many records are still only viewed by browsing the collection. There are over 295,000 images available. The records are listed by parish.
These are great sources but what if you don’t know which parish your ancestors attended. The Archdiocese of Chicago website under genealogy resources https://archives.archchicago.org/geneology-resources provides a copy in pdf format of the book by Jack Bochar Locations of Chicago Roman Catholic Churches, 1850-1900. The book has detailed maps of parish locations in Chicago by date. To use this book, locate your ancestors first using city directories and then plot their address(es) on the map based on the time period. (Reminder - Chicago street numbering changes were in 1909 and 1911 and street name changes occured). It is recommended to trace their location over a period of time recording each address in case they moved around a lot. You will be able to see which parishes were in the neighborhood. Then you can browse those parish records. If you don’t have luck with the closest parish, then expand your area and look at the next several parishes. Happy researching!