  The emergence of the ISR project at CERN is described in the light of the
situation at CERN at the end of the 1950s when the CERN Proton Synchrotron (PS)
was still under construction. The discussions leading to the project are put
into context with world-wide efforts to build larger and more powerful
accelerators at that time; the evolution of the project before approval is
sketched. The basic design considerations and the most significant
technological choices are explained. The construction period is summarized by
highlighting important milestones and the performance achieved during
commissioning in 1971, the first year of running, is given.
