Spoiler alert: This post is boring (but may be useful to some people).
The Chicago Municipal Code is a one- to three-volume book that provides a subject arrangement of Chicago ordinances of a general and permanent nature. It is essentially an encyclopedia of Chicago law.
People are interested in the historical codes for reasons legal, practical and historical. For example, I can find out why my two-flat has a stone foundation and why the second story is larger than the first. Both were required by code in 1908. The first floor had to be three bricks thick, and the second only two bricks thick. Another popular question: “When did cross dressing become illegal, and when was it legalized?” Answer: the ban appeared in the Municipal Code by 1851, and it was repealed in 1978.
The current Chicago Municipal Code is online, and we have paper copies at the library. It gets updated every six months or so. It also gets a major rearrangement and renumbering every 10 to 60 years. CPL’s Municipal Reference Collection has almost all of the versions starting with the first from 1837. We can use the Journal of the Proceedings of the City Council to help reconstruct the code for dates between published codes.
The Zoning Ordinance has been published separately since it first passed in 1923. For a few years it also appears in the Municipal Code.
The Building, Fire and Electrical Codes are all contained in the Municipal Code, but also published as separate volumes. The Building Code has been published since about 1900 at more frequent intervals than the Municipal Code. It might be easier to use for building questions. Some years are in Hathitrust or the Internet Archive.
The Special Ordinances of Chicago were published in 1915, but not since. They were included in some earlier codes. Whereas the Municipal Code has ordinances of a general and permanent nature, the Special Ordinances deal with specific corporations—usually granting a franchise or detailing how a railroad may run its tracks. I have been unable to find them online, but we have them in paper.
Not much is available in the way of legal interpretation for the code. One city-issued publication is the Opinions of the Corporation Counsel and Assistants (1872-1983, some years of Opinions of the Corporation Counsel and Assistants available online). CPL does not have case law, but especially if you are trying to find early cases, it may be helpful to check Illinois Law and Practice and Shepard’s at a law library.
Committee hearings and reports are rarely available and tend to be of more interest to historians than lawyers. It is worth checking the original ordinance as passed in the Journal of Proceedings. Sometimes there is "WhereAs" wording.
Prior to 1872, Chicago had its own charter, a state law giving the city certain specific powers. Chicago has operated under the Illinois Cities and Villages Act since 1872. The charter is usually included in the code.
Known Editions of the Code
These editions of the Municipal Code are all available in paper in the Municipal Reference Collection with the exception of the 1839 and 1843 codes. We also have a number of supplements and updates not listed. I have included links to the editions that are available online.
- The Laws and Ordinances of the City of Chicago 
- The Laws and Ordinances of the City of Chicago  1839 available in print only at Chicago History Museum
- Amendments to the City Charter, 1837-41; and, Laws and Ordinances of the City of Chicago, passed in Common Council since June 19, 1837, ... and in force December 1, 1843 1843 available in print only at Chicago History Museum
- Charter of the City of Chicago, and Amendments. With Rules of Council and Ordinances 
- The Revised Charter and Ordinances of the City of Chicago 
- Ordinances of the City of Chicago: Passed Since the Publication of the Revised Ordinances of 1851 
- The Charter and Ordinances of the City of Chicago (to Sept. 15, 1856)
- An Act to Amend the Act Entitled "An Act to Reduce the Law Incorporating the City of Chicago ... with, the Ordinances of the Common Council, Passed from September 22, 1856, to April 5, 1858
- Laws and Ordinances Governing the City of Chicago, January 1, 1866
- Laws and Ordinances Governing the City of Chicago 
- The Municipal Code of Chicago 
- 1887 Supplement
- Laws and Ordinances Governing the City of Chicago As in Force April 2, 1890
- The Revised Municipal Code of Chicago of 1905
- The Chicago Code of 1911
- The Chicago Municipal Code of 1922
- Revised Chicago Code of 1931
- Municipal Code of Chicago: ..., August 30, 1939 With Amendments: The 1939 volume was issued as a hardback. A loose-leaf version soon followed.
- The Municipal Reference Collection has retired volumes of the loose-leaf annually for 1943 to 1984. Thus we have copies of the 1956, 1957,1958, etc. The code was not published 1985 to 1989, but our 1984 code is annotated with the code changes for those years.
- Municipal Code of Chicago 1990 to Date: The code was renumbered in 1990. We have retired loose-leaf versions every several years, allowing you to reconstruct the wording of the code at any given point of time.