 In 1900, Pillsbury incorporated Standard Oil of California—the company would later become Chevron, which has remained one of the firm's longstanding clients.Pillsbury managed Chevron's then-record $13.2 billion cash merger with Gulf Oil in 1984, its 2001 merger with Texaco and its 2005 acquisition of Unocal Corp.

Pillsbury is the result of several law firm mergers.In 1990, Pillsbury, Madison & Sutro merged with Los Angeles-based Lillick & McHose, and then in 1996 with Washington, D.C.-based Cushman Darby & Cushman.