The theoretical solid-state physicist Walter Kohn was awarded one-half of the 1998 Nobel Prize in Chemistry for his mid-1960's creation of an approach to the many-particle problem in quantum mechanics called density functional theory (DFT). In its exact form, DFT establishes that the total charge density of any system of electrons and nuclei provides all the information needed for a complete description of that system. This was a breakthrough for the study of atoms, molecules, gases, liquids, and solids. Before DFT, it was thought that only the vastly more complicated many-electron wave function was needed for a complete description of such systems. Today, fifty years after its introduction, DFT (in one of its approximate forms) is the method of choice used by most scientists to calculate the physical properties of materials of all kinds. In this paper, I present a biographical essay of Kohn's educational experiences and professional career up to and including the creation of DFT. My account begins with Kohn's student years in Austria, England, and Canada during World War II and continues with his graduate and post-graduate training at Harvard University and Niels Bohr's Institute for Theoretical Physics in Copenhagen. I then study the research choices he made during the first ten years of his career (when he was a faculty member at the Carnegie Institute of Technology and a frequent visitor to the Bell Telephone Laboratories) in the context of the theoretical solid-state physics agenda of the late 1950's and early 1960's. Subsequent sections discuss his move to the University of California, San Diego, identify the research issue which led directly to DFT, and analyze the two foundational papers of the theory. The paper concludes with an explanation of how the chemists came to award "their" Nobel Prize to the physicist Kohn and a discussion of why he was unusually well-suited to create the theory in the first place.Emil Eliezer Nohel (ca. 1938) was a high school physics teacher who inspired Kohn to become a scientist. Courtesy of the Yad Vashem Photo Archive.Dean Samuel Beatty (ca. 1953) bent the admission rules so Kohn could enter the University of Toronto. Courtesy of the University of Toronto Archives.