Origins in Chicago
The firm that was to become Sidley Austin was formed in Chicago in 1866 by Norman Williams and John Leverett Thompson as the partnership of Williams & Thompson. One of the nascent firm's first clients was the
Pullman Company, the manufacturer of specialty sleeping railway cars. Other early clients included
Western Union Telegraph Company, which moved its Midwest headquarters from Cleveland to Chicago in 1869. After the
Great Chicago Fire of 1871, the firm represented numerous insurance companies including
Equitable Life Assurance Society. In 1892, William Pratt Sidley joined the firm after having earned an
LLB from Union College of Law and a
Harvard Law School. By 1913, the firm's name was changed to Holt, Cutting & Sidley, although Sidley would be the guiding personality for the Chicago firm through the 20th century. Three years later—the firm then fifty years old—had four partners, four clerks (associates), and ten staff employees with gross income of around $100,000 (roughly $1.9 million in 2008 dollars).
Buffeted by the
Great Depression, the firm experienced a dramatic fall in revenues until the
New Deal in the 1930s reinvigorated the capital markets. The firm represented
Halsey, Stuart & Co., a Chicago-based
underwriter in one of the first transactions under the
Securities Act of 1933. In 1944, the name was changed to Sidley, Austin, Burgess & Harper and shortened to Sidley & Austin in 1967.
Towards a national firm
Second World War, Sidley & Austin began expanding beyond its Chicago roots as many of its clients entered new markets. In 1963, its
Washington, D.C. branch was established which would soon become an important player in that city's legal market through its representation of the
American Medical Association,
American Bar Association and the International Minerals & Chemical Corporation. The firm developed strengths in antitrust and the representation of clients in front of the
Federal Trade Commission.
Sidley & Austin was among several law firms caught up in the
Savings & Loan Crisis and paid $7.5 million to settle
legal malpractice claims stemming from its representation of the
Lincoln Savings and Loan Association. Such legal work was profiled in the book by
Ralph Nader and Wesley J. Smith, No Contest: Corporate Lawyers and the Perversion of Justice in America.
Expansion and consolidation
Sidley & Austin expanded tremendously in the 1970s and 1980s. In 1972, the firm merged with the 50 lawyers of Chicago firm Leibman, Williams, Bennett, Baird & Minow. Offices were established in London, Los Angeles, Singapore and New York in short order.
In 2001, the firm merged with
Brown & Wood, a New York-based law firm established in 1914 with 400 attorneys additional domestic offices in Washington, D.C., San Francisco and Los Angeles and overseas branches in London, Beijing and Hong Kong (where it practiced English law in addition to U.S. law). Brown & Wood was known for its
structured finance and
securitization practices. The firm's well-regarded publication, Accessing the U.S. Capital Markets: An Introduction to United States Securities Law, continues to be updated annually today. Brown & Wood had offices in the
World Trade Center. The firm was known as Sidley Austin Brown & Wood until the name was rebranded as Sidley Austin in 2006.
Appellate Practice Group
U.S. Solicitor General
Rex E. Lee founded Sidley Austin's Appellate Practice Group to represent clients in all appellate courts, including the United States Supreme Court, the federal courts of appeals, and state appellate and supreme courts. Following Lee's death, the group was led by Carter Phillips, who has argued more cases before the Supreme Court than any lawyer in private practice
 and who now chairs the firm's executive committee.
 The current co-chairs of the practice group are former Acting Attorney General
Peter Keisler and former Principal Deputy Associate Attorney General Joseph Guerra.
The Appellate Group has argued several landmark cases before the Supreme Court including
U.S. Term Limits, Inc. v. Thornton (constitutionality of state-imposed term limits on members of Congress),
Missouri v. Jenkins (proper role of federal courts in imposing desegregation remedies), and
United States v. Lopez (Commerce Clause challenge to a federal statute prohibiting the possession of firearms within 1,000 feet of a school).
 Directly or indirectly, Sidley Austin plays a role in 40 percent of the cases the Supreme Court hears every term. Over the last 30 years, its lawyers have argued 115 high court cases.
On March 19, 2015 the
U.S. Court of Appeals for the Federal Circuit ruled that a client of Sidley Austin,
AT&T Inc., filed its appeal too late in a patent infringement case, which cost AT&T its right to appeal a $40 million adverse judgment. The Federal Circuit held that a team of lawyers from the firm failed to file a notice of appeal within the requisite thirty days after a federal district court denied several post-trial motions. The court affirmed the district court's ruling that it was "troublesome" that none of the eighteen lawyers and assistants who received the electronic notices "bothered to read the orders issued by the court."