Early in 1915 E. L. DeGolyer advanced the idea of organizing Southwest geologists. A meeting at Tulsa, called by J. E. Thomas, resulted in a conference at Norman and formation of the A.A.P.G. About a year later formal organization was perfected with Thomas as president. Minutes and recollections of early meetings and reports of progress are included in the chapter on founding and formative years (1915-20). Years of growth (1927-41) evidenced expansion of research, formation of committees, and organization of related societies. War years were marked by founding of the American Geological Institute and formation of new committees. Post-war expansion (1947-58) showed an increase in membership and association activities. Membership at end of 1965 was 15,126, and there has been no abatement in expansion of services. Short memorials of deceased past presidents and a list of publications are included.