The purpose of this paper is to demonstrate that military and defense related research and procurement have been a major source of commercial technology development across a broad spectrum of industries that account for an important share of United States industrial production. I discuss the development of five general purpose technologies: (1) military and commercial aircraft, (2) nuclear energy and electric power, (3) computers and semiconductors, (4) the Internet, and (5) the space industries. The defense industrial base has become a smaller share of the industrial sector which is itself a declining sector in the U.S. economy. It is doubtful that military and defense related procurement will again become an important source of new general purpose technologies. When the history of U.S. technology development for the next half century is eventually written it will almost certainly be written within the context of slower productivity growth than the relatively high rates that prevailed in the U.S through the 1960's and during the information technology bubble that began in the early 1990's.