Abstract The response spectrum method (RSM) in earthquake engineering was conceived and then fully developed by M.A. Biot (1905–1985) during the period of about 10 yr, between 1932 and 1942. On the occasion of the 100th anniversary of Biot's birth, this paper reviews his contributions to earthquake engineering, and then briefly outlines the milestones in the later evolution of the RSM, and the eventual introduction and acceptance of the method by the engineering disciplines in the early 1970s. The role of the Biot spectrum in the formulation of design codes is illustrated briefly, using examples from code development in California. Finally, the limitations of the linear response superposition method are discussed, and future directions for the development of earthquake-resistant design tools are suggested.