Total Immersion in Computing

March of 2022 marked the 70th anniversary of the MANIAC, the first all-electronic computer at Los Alamos. Construction of the MANIAC began at a time when electronic computers numbered only in the single digits worldwide, making each new system an important contributor to the computing field. Los Alamos played an outsized role in this development, with the MANIAC's first programmers and operators, many of whom were women who had worked as human computers, pioneering many of the methods and concepts that are now commonplace. When completed, the MANIAC became the Lab's frontline for cutting-edge numerical simulations that made possible the rapid development and testing of atomic and thermonuclear weapon designs that occurred during the 1950s. Test results were then used to calibrate the computer models to improve their capabilities. The simulation technologies and methods pioneered with the MANIAC became particularly critical for the Lab's weapons program when the 1958 moratorium halted testing, and computational modeling had to fill much of the resulting gap. In celebrating the MANIAC, this talk also celebrates the hard work and ingenuity of the people at Los Alamos who helped to invent the modern field of scientific computing, using vacuum tubes and paper tape to build a legacy that continues at the Lab today.