This article describes the development and construction of the first generation of synchrotrons by their American developer, Edwin McMillan. A synchrotron is a high-energy particle accelerator, similar to a cyclotron, in which the magnetic field and/or the frequency are fluctuated during acceleration. McMillan relates how he arived at the idea for the synchrotron, and he describes the institutional process that his proposed project underwent to obtain approval. He details the construction and use of the synchrotron at Berkeley that he oversaw and the later development of the proton synchrotron. He also discusses the work of other physicists who were independently developing their own versions of the synchrotron at the same time.