This Memorandum describes the thirteen-year life of the JOHNNIAC computer, a Princeton-class machine designed and built at the RAND Corporation in 1953. The history presented here is based on documents and recollections of the individuals involved in the creation of JOHNNIAC, and includes a definitive paper coauthored by mathematician John von Neumann, for whom JOHNNIAC was named. The author, while at The RAND Corporation, was associated closely with various studies made with the aid of JOHNNIAC. He is presently a RAND consultant, and a Professor in the Department of Accounting at San Fernando Valley State College.