Cravath, Swaine & Moore is a major Wall Street law firm that traces its beginnings to the law practice begun by William H. Seward (1801-1872) in Auburn, New York, in 1823. It assumed its current character when Paul D. Cravath (1861-1940) joined the firm of Seward, Guthrie & Steele in 1899.

Paul Drennan Cravath was born in Berlin Heights, Ohio, on July 14, 1861. He graduated from Columbia University Law School in 1886 and joined the New York bar, becoming senior partner in Cravath & Houston in 1891. The firm dissolved in 1899 when his law partner returned to teaching, and Cravath was offered a partnership in the Seward firm under the style of Seward, Guthrie & Steele. Charles Steele (1857-1939) left the firm at the end of 1900 to become a Morgan partner, and it was restyled Guthrie, Cravath & Henderson. Guthrie and some of the other old Seward partners withdrew over personal differences in 1906, and the firm became Cravath, Henderson & de Gersdorff. The style of the partnership changed successively to Cravath & Henderson (1913-1920); Cravath, Henderson, Leffingwell & de Gersdorff (1920-1923); Cravath, Henderson & de Gersdorff (1923-1928); Cravath, de Gersdorff, Swaine & Wood (1928-1944); and to its current form of Cravath, Swaine & Moore on March 1, 1944.

Building on the ideas of others, Cravath devised the organization of the modern corporate law office, the so-called "Cravath system." Cravath recruited the best graduates of the best law schools who would work for a few years as associates. Future partners were selected from the best associates, and the rest were expected to move on to other firms while they were still young. The associates were drilled in the methods and culture of the Cravath firm, which involved hierarchy and the division of labor, thus ensuring uniformity of practice.

The development of the Cravath system paralleled similar trends toward professionalization and bureaucraticization that were occurring elsewhere in the business world. The Cravath firm was thus particularly well-placed to play a role in the industrial combinations of the turn of the century and in helping business to cope with the growth of federal and state regulation and the antitrust movements of the Progressive Era. Early clients of the Cravath firm included the Westinghouse Companies and the banking house of Kuhn, Loeb & Company. Through the latter, it had ties to E. H. Harriman (1848-1909), while it also maintained close relations with the House of Morgan. The firm played an important part in railroad reorganizations and the court-imposed breakups of the Harriman Lines and the Reading Combination. It acted as legal midwife in the birth of Bethlehem Steel and International Harvester, and in the building of the Interboro Rapid Transit subway and the unification of the Manhattan surface transit system. The firm also took an interest in the early motion picture industry, before it relocated to California, and was later associated with the Loews entertainment empire and the formation of RCA.