Look for an Article

In many instances, a law review article may discuss the legislative history of your statute, saving you the trouble of examining each individual document.  Thus, one helpful strategy is to begin by Keyciting (Westlaw Edge) or Shepardizing (Lexis+) your statute and then looking at citing law reviews. Once you're in the Citing References, narrow to secondary sources then run a "Search Within" to search only the secondary sources (i.e. law reviews) that have cited to your statute. A good search syntax in Westlaw: ATLEAST5("legislative history")  Running that search within the filtered citing references will retrieve secondary sources that have at least five instances of the phrase "legislative history" in the article. You could broaden this search to opinions; occasionally you get lucky and find a court opinion discussing the legislative history of a statute. Taking the time to search for an article or court opinion with this kind of discussion is a worthwhile first research step.

Consult a Research Guide for Steps and Sources

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• The best source for any municipal legislative materials is the Journals of the Proceedings of the City Council, which are available online from 1981-present. You can also access Council Reports back to 2006 online. The Electronic Legislative Management System (eLMS) provides online access to Chicago City Council legislation and records between December 1, 2010 and present. 
• Search Chicago newspapers contemporary to when the ordinance was being created. NU has many newspaper databases. Depending on how old it is, ProQuest Historical Newspapers (full-text historical articles from several major U.S. newspapers, including the Chicago Tribune (1849-1993) and Chicago Defender (1909-1975) and ProQuest US Newsstream (current U.S. news content and archives that stretch back into the 1980s). Check the coverage dates and filter off titles you don’t want included in the results.
• Chicago Public Library has the Municipal Reference Collection at the Harold Washington branch. “The Municipal Reference Collection at Harold Washington Library Center chronicles almost every aspect of municipal life in Chicago, housing most City of Chicago documents published since the mid-1800s as well as documents from other local agencies such as the Chicago Board of Education and the Chicago Transit Authority.” They have a lot of materials that are not discoverable in the CPL library catalog. Contact their Reference Desk at (312) 747-4526 or submit a question online.