Released in October 2004, the work is the result of a ten-year collaboration between the Newberry Library and the Chicago Historical Society.

[2] The print edition is 1117 pages and includes 1400 entries, 2000 biographical sketches, 250 significant business enterprise descriptions, and hundreds of maps.

At the time, Grossman was the vice president for research and education at the Newberry Library and visiting professor of history at the University of Chicago.

[11] After Grossman and Keating obtained the initial grant, Reiff, a historian with computer expertise, and encyclopedia veteran Carol J. Summerfield all became part of the team.

[5] The editors sought the advice of Chicago-area librarians who were organized into focus groups to determine the proper components for the planned publication.

[10] Early on they sought the expertise of University of Chicago cartographer Michael P. Conzen, who helped develop 56 original maps.

The longest biographical entries, about 450 words, were written for former Chicago Mayors Harold Washington and Richard J. Daley.

[7] By 1998, the editors had settled on the table of contents and begun the job of assigning, editing, fact-checking and re-editing the hundreds of entries, some of them as long as 4000 words.

[13] Using press releases from the Copley News Service,[14][15] the book was widely publicized throughout the state of Illinois,[16][17] and it was even reviewed by The Wall Street Journal.

[20][21] Major funding for the $65 list price four-color print version of the publication, which cost $1.7 million in the end, was provided by the NEH, the MacArthur Foundation, the City of Chicago and the State of Illinois.

[22] The electronic edition made Chicago the second major U.S. city (following Cleveland) with an extensive Internet encyclopedia dedicated to its history and its release was covered by newspapers throughout the Midwest.

[10] The State Journal-Register, the Springfield, Illinois newspaper, reviewers complain that downstate cities and regions are neglected in the book.

[25] The Peoria Journal Star notes that although there are complaints about omissions and underserved topics, the online version should quell the demands for further knowledge.

[22] Journal of American History along with the website History Matters: The U.S. Survey Course on the Web published a review by University of Southern California professor Philip J. Ethington that spoke glowingly about both versions of the encyclopedia describing it as "one of the finest collective works (with 633 listed authors) of North American historical scholarship of our era".

However, the review notes that the online version provides "powerful and substantive" interactive resources that are not possible in the print edition.

[3][10] The 1400-entry main alphabetical section of the Encyclopedia covers all Chicago neighborhoods, suburbs, and ethnic groups as well as the major cultural institutions.

Topics covered include technology and science, architecture, religions, immigration, transportation, business history, labor, music, health and medicine.

It is considered the most geographical diverse city encyclopedia of its kind because it fully encompasses the suburbs in eight of the region's counties.

[2][3] There are separate lengthy interpretive essays woven into the alphabetical section on topics such as the built environment, literary images of Chicago, and the city's sports culture.

The Encyclopedia includes a 2000-entry comprehensive biographical dictionary and a detailed listing of approximately 250 of the city's historically significant business enterprises.