[9] Among the firm's first clients were the Pullman Company, the manufacturer of specialty sleeping railway cars, as well as Western Electric and Illinois Steel.

[9] In 1963, former postmaster general J. Edward Day left the administration of President John F. Kennedy to establish the firm's Washington, D.C.

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.

Sidley has received the most First-Tier National Rankings a total of eight times since the inception of the U.S. News & World Report Best Law Firms Survey in 2010.

[25] The firm earned the top spot in Asset-Backed Alert's 2019 league tables for most active underwriter counsel in U.S. asset- and mortgage-backed securitization transactions.

[26] Other honors include the American Bar Association's 2019 Champions for Disability Inclusion in the Legal Profession Award,[27] conferred in recognition of the firm's measurable progress in recruiting, retaining, and advancing to leadership lawyers with disabilities, and being named a 2019 "Litigation Department of the Year" finalist by The American Lawyer.

[31] Its appellate and US Supreme Court practice is also particularly well known and has been featured in USA Today, BusinessWeek, the American Lawyer, the Legal Times, and the National Law Journal.

[28] In 2020, Sidley was named "Firm of the Year" in Capital Markets (Overseas); Corporate Compliance; Healthcare, Pharma and Life Sciences; and Real Estate and REIT by China Business Law Journal.

[33] Sidley Austin partner George Fatheree worked pro bono on behalf of the descendants of Willa and Charles Bruce[34] to execute the return of beachfront land which had been seized by Los Angeles authorities in the 1920s.