The development history of the Westinghouse J34 workhorse engine is presented in detail. Major design changes from earlier models and as well as those introduced during early development are covered. The lengthy effort to reach the guaranteed 3,000-pound thrust level are explained in detail. With BuAer finally stepping in to contain out of control unique airframe installation demands from each of the airframe manufacturers, initial production was established. The J34-WE-22 model was produced in five installation variations to meet the airframe schedules from Vought, McDonnell, and Douglas. Service use revealed the need for extensive continuing development and the steps to achieve improved models offering small increases in thrust, greater reliability, improved fuel consumption, and better engine control at higher and higher altitudes is traced through the release of the many sub-models. The early attempts to match the J34 to afterburners and the difficulties encountered is explained including the little known J34-WE-11 design for the Air Force. Emerging into an era of rapid change in the demands for much higher power for interceptors and all- weather fighters, the engine soldiered on and was used in the U.S. carrier fleet until beginning to be replaced in the late 1950’s. The last version of the engine, the J34-WE-48, introduced Rolls-Royce technological improvements and it powered the initial versions of the North American T2J-1 Buckeye single engine trainer beginning in 1960. The author has again used primary sources to compile this history, including many tables, 196 pictures and figures. 386 B&W pages.