The American Physical Society has designated UC San Diego’s Mayer Hall as a historic site in recognition of research conducted by physicists Walter Kohn and Lu Jeu Sham on density functional theory. Their development of the “Kohn-Sham equation” inside Mayer Hall became the foundation for the computation of the material properties of electrons and nuclei. Understanding the electronic properties of complex systems is essential to the design and engineering of new materials and drugs. Kohn and Pierre Hohenberg on sabbatical in Paris developed a theorem for the electron ground state energy to depend on the electron density distribution instead of the usual potential energy due to the nuclei. In Building C (later named Mayer Hall), from 1964-66, Kohn and Sham laid the foundation of a computation method, based on a single-particle equation composed of its quantum kinetic energy and the potential energy including the interaction effects.