This is a really great connection but my Sidley Austin links aren't yielding much...

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

In 1972, the firm merged with the 50 lawyers of Chicago firm Leibman, Williams, Bennett, Baird & Minow. Additional offices were then established in London, Los Angeles, Singapore and New York. Following the merger, Washington D.C. partner Day resigned and later sued the firm, In a 1974 lawsuit, Day alleged that the merger represented a "breach of fiduciary duty, breach of contract, fraud and misrepresentation, conspiracy, wrongful dissolution or ouster of co-partner and breach of partnership agreement." The suit was later dismissed with prejudice.[12]

^ Hmm, hostile takeover in 1972?

In 2001, the firm merged with Brown & Wood, a New York-based law firm established in 1914 with 400 attorneys and 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 securities, structured finance and securitization practices. Brown & Wood had offices in the World Trade Center on floors 54 and 56-59.[13]

9/11 connection?

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.

^ Savings & loan crisis connection