American economist and anthropologist whose book The Races of Europe: A Sociological Study (1899) directed the attention of American social scientists to the existence of subdivisions of “geographic races.” Specifically, Ripley asserted that the European Caucasians can be broadly classified into three local races: the northern (Teutonic) and southern (Mediterranean) populations are probably of extremely ancient origin, but the central (Alpine) group has descended from more recent migrants from Asia. This division followed trends in European anthropology initiated by Arthur Gobineau in the mid-19th century.

Ripley was trained in civil engineering at the Massachusetts Institute of Technology and in political economics at Columbia University, New York City (Ph.D., 1893). He spent most of his career as professor of political economy at Harvard University (1902–33). During World War I he served as administrator of labour standards for the U.S. War Department. In 1920–23 he drew up for the Interstate Commerce Commission the Ripley Plan for the regional consolidation of U.S. railways. In 1931–32, while testifying before the U.S. Senate, he advocated close federal restraint on investment trusts and on the financial practices of large business corporations.