This book provides a detailed account of the development, design, construction, and initial operation of the Experimental Breeder Reactor-II (EBR-II) and the associated pyrometalurgical processing facility. This firsthand account includes a detailed presentation of the design and construction of the reactor, as well as numerous original drawings and photographs. Explanations of certain design choices are provided, as well as experiences gained with the EBR-II. Also of general and historical interest, the book includes an appendix that traces the lineage of EBR-II, beginning with Erico Fermi and Walter Zinn and progressing to the EBR-II project.