This law firm traced its roots to Williams & Thompson, a Chicago firm founded in 1866 by Norman Williams and John L. Thompson. The name Sidley—from William Pratt Sidley, who started working for the firm as a young lawyer in 1892—entered the firm's title in 1900, when it became Holt, Wheeler & Sidley. Edwin C. Austin joined the firm in 1914. By this time, the firm's list of clients included many of Chicago's largest businesses, including Pullman, Western Electric, and Illinois Steel. In 1916, the firm consisted of nine lawyers and their office staff. In 1920, the firm's offices moved from the Tacoma Building to the Roanoke Building, a newer skyscraper. By 1941, when the firm was known as Sidley, McPherson, Austin & Burgess, it employed 32 lawyers. From 1950 to 1967, the firm was called Sidley, Austin, Burgess & Smith. In 1967, when it changed its name to Sidley & Austin, it consisted of 80 lawyers, half of whom were partners; two years later, the firm moved into new offices at One First National Plaza, a new skyscraper in Chicago's Loop. A 1972 merger with Liebman, Williams, Bennett, Baird & Minow, another large Chicago law firm, created a firm of 150 lawyers. Over the next 25 years Sidley & Austin grew to rank consistently as one of Chicago's largest law firms and opened offices in other cities around the country. In 1999, it merged with competitor Brown & Wood to become Sidley, Austin, Brown & Wood LLP. Under its new name, the firm claimed 400 attorneys and 1,400 staff in its Chicago headquarters alone, with fourteen additional offices nationwide.

This entry is part of the Encyclopedia's Dictionary of Leading Chicago Businesses (1820-2000) that was prepared by Mark R. Wilson, with additional contributions from Stephen R. Porter and Janice L. Reiff.