The Hanford Site in southeastern Washington state was built by the Army Corps of Engineers and the DuPont Corporation during World War II to produce plutonium for America's first atomic weapons. The gigantic facility was immediately successful, producing and delivering in less than two years the plutonium for the world's initial atomic explosion and for the bomb dropped on Nagasaki that effectively ended World War II. This first complete history of Hanford was made possible by the recent declassification of tens of thousands of formerly secret government documents relating to the construction, operation, and maintenance of the site. It describes the releases (planned and accidental) of radioactive and chemical contaminants; their pathways through the environment; attempts to correct problems under conditions of rapid, nearly chaotic change; and the secrecy of government operations that made scientific review of Hanford processes virtually impossible.