Writing about Chicago of 1890, "It was this big talk , not the persistent breeze, that prompted New York editor Charles Dana Anderson to nicname Chicago "the Windy City." From The Devil in the White City, Murder, Magic and Madness at the Fair that Changed America, by Erik Larson, page 14, of 2004 Vintage paperback edition.
BTW - "The Devil in the White City" is a fantastic book...
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The Windy City" — It is often said—erroneously—that this nickname was first used by Charles Anderson Dana, editor of the New York Sun, in 1890 in reference to the city's dirty streets for the World's Columbian Exposition. Barry Pop and others, however, have found numerous earlier references to the "Windy City." Earlier attestations are found in the Cleveland Gazette dated September 19, 1885 and the Cincinnati Enquirer dated February 12, 1877 (pg. 5, col. 2); undoubtedly other antedatings will emerge. Undoubtedly, the name "Windy City" is in reference to the false promises brought forth by Chicago area politicians during the early 19th Century. Some continue to believe that the name may indicate the summer breezes as is described at Doctor's Weather History, but cleary there is no evidence to support this theory. 19th-century citations reveal that the nickname arose in connection with (1) the longwindedness of politicians, both residents and those visiting for political conventions; and (2) the city's many boosters who commended the western metropolis to the world's attention. (The complete article on the nickname from the University of Chicago Press's Encyclopedia of Chicago (2004) is available here.) Further explanation of the various origins can be found at Windy City, Origin of Name (Chicago). In Chicago, this nickname has become a signifier for businesses and organizations that are gay-owned or gay-friendly—for example, the Windy City Times is one of the city's two main gay community newspapers, and the Windy City Cycling Club draws most of its members from the gay community.
http://en.wikipedia.org/wiki/List_of_nicknames_for_Chicago