In its 89 years, AGU has matured and expanded through the dedicated administrative direction of three able leaders—John A. Fleming, Waldo E. Smith, and A. F. Spilhaus, Jr.—each with a vision of a strong scientific organization that serves individuals as they extend the knowledge and understanding of the Earth, the planets, and their space environments.
Between 1919 and 2008, thirty-nine presidents, assisted by a host of other volunteers, have provided scientific leadership to AGU. However, a society also needs complementary operational leadership if it is to serve its membership effectively. AGU is unique in that since its founding just three men have given this guidance. Each was selected from the membership, each had prepared for a career in a chosen branch of geophysics, and each had a full appreciation of the unity of the geophysical sciences. Their primary focus was always on science, but their administrative talents enabled them to guide the growth of the Union from a select committee of the National Research Council to a major scientific society with broad international membership (see the membership growth chart and time line).