In March 1945 a Japanese paper balloon bomb drifted across the Pacific, hit a power line in Washington State, and triggered an automatic shutdown of a secret nuclear reactor whose workers did not know what they were building. This episode tells the story of the Hanford Site, a 586-square-mile stretch of desert that went from farmland and ancient indigenous fishing grounds to the birthplace of the plutonium used in the Trinity test and the Nagasaki bomb. It explains why the Manhattan Project chose the site, how the government used the Second War Powers Act to evict thousands of farmers and displace the Wanapum, Yakama, Nez Perce and Umatilla tribes, and why DuPont agreed to build it for a fee of one dollar.

From the B Reactor's 1,200-ton graphite core and 30,000 gallons of Columbia River water per minute to the windowless concrete separation ...