AdA:The First Electron-Positron Collider

I review the origin of AdA, the first electron-positron collider at Frascati, Italy, in the early 1960s. I describe the problems that were tackled to produce the positron beam, the vacuum, and the injection system that were necessary to observe the electron-positron beam-beam collisions. Accidents and incidents occurred, such as the unpredicted "Touschek effect," and were surmounted. I discuss the roles of the physicists involved in this work and the state of physics at the time, and I sketch subsequent work on larger collider rings. My recollections are based on the original literature and unpublished documents, photographs, and drawings.