The Encyclopedia of Chicago is an historical reference work covering Chicago and the entire Chicago metropolitan area published by the University of Chicago Press. Released in October 2004, the work is the result of a ten-year collaboration between the Newberry Library and the Chicago Historical Society. It exists in both a hardcover print edition and an online format, known as the Electronic Encyclopedia of Chicago. The print edition is 1117 pages and includes 1400 entries, 2000 biographical sketches, 250 significant business enterprise descriptions, and hundreds of maps. Initially, the internet edition included 1766 entries, 1000 more images and sources.