This paper reviews the life, work, and profound impact of William Alonso, covering not only the genesis and substance of his doctoral dissertation, and the resulting 1964 book that has become a cornerstone of the urban economics literature, but also his diverse and original contributions across other domains. These encompass the education of planners, the integrity of statistical data, the “five bell shapes” of development, multi-regional demographic accounting, the concept of “borrowed size” in city networks, and his ground breaking general theory of mobility and migration. Alonso was mostly an ideas person, with a strong affinity to interdisciplinary research. He prioritized the logical consistency of conceptual contributions over empirical validation, or the minutiae of mathematical extensions. Many areas of his work offer scope for path breaking contributions by new generations of scholars. Specifically, his theory of movements appears to have been underappreciated to date due to apparent difficulties in operationalizing the general framework. Nevertheless, with today’s advanced computing capabilities and enhanced data availability, his theory of movements offers potential for significant breakthroughs in migration and social mobility modeling. The paper concludes by positing that Alonso would have advocated for a holistic approach to tackling contemporary global challenges, urging regional scientists to go beyond the confines of individual academic silos towards more integrated and impactful scientific endeavors.