Harold Brown was a child prodigy born to secular Jewish parents Abraham Brown, a lawyer and World War I veteran, and Gertrude Cohen Brown, a bookkeeper, in Brooklyn, New York. He graduated from the Bronx High School of Science at age 15 and attended Columbia University, earning an A.B. summa cum laude in physics in 1945, an M.S. in 1946, and a Ph.D. in physics in 1949 under advisor Isidor Isaac Rabi. His early career centered on nuclear physics, with positions at the Radiation Laboratory at UC Berkeley and as director of Lawrence Livermore National Laboratory from 1960 to 1961. He served as a consultant to the President's Science Advisory Committee and a delegate to the Strategic Arms Limitation Talks. Brown held key government roles, including Director of Defense Research and Engineering from 1961 to 1965 and Secretary of the Air Force from 1965 to 1969. He was president of the California Institute of Technology from 1969 to 1977 before serving as U.S. Secretary of Defense from 1977 to 1981 under President Jimmy Carter. In that position, he significantly increased defense budgets, supported the controversial MX missile deployment, and developed the countervailing strategy in Presidential Directive 59, which drew criticism for potentially escalating nuclear risks; he faced accusations of leaking PD-59 details and stealth technology to support Carter's 1980 re-election, though no legal actions ensued. After government service, Brown was a visiting professor at Johns Hopkins University, chaired its Foreign Policy Institute, and served on corporate boards including Altria. He received the Presidential Medal of Freedom in 1981 and the Enrico Fermi Award in 1993. Married to Colene Dunning McDowell since 1953 until her death in 2018, he had two children and resided in Rancho Santa Fe, California, at the time of his death from pancreatic cancer.