The Manhattan Project to develop the first atomic bomb was, perhaps, the greatest assemblage of scientists and engineers in history. Many of the participants had already established their places in scientific history before becoming members of the project. For the younger participants the project provided an unfettered environment for their research that shaped the remainder of their careers. This course will explore the prior work that brought great established scientists (e.g., Robert Oppenheimer, Neils Bohr, Hans Bethe, Enrico Fermi, Edward Teller, Ernest Lawrence, John von Neumann) to Los Alamos and the renowned scientists (e.g., Richard Feynman, Glenn Seaborg, Luis Alvarez, John Archibald Wheeler, Wolfgang Panofsky) whose future careers were shaped there. It will also describe the unprecedented scientific, engineering, and ethical problems the team faced in the design, testing and execution of “the gadget.” The course will present a balanced mixture of the history and science that defined the beginning of the nuclear age.