The Hanford Site is a decommissioned nuclear production complex operated by the United States federal government on the Columbia River in Benton County in the U.S. state of Washington. The site has been known by many names, including Hanford Project, Hanford Works, Hanford Engineer Works and Hanford Nuclear Reservation.
Established in 1943 as part of the Manhattan Project in Hanford, south-central Washington, the site was home to the B Reactor, the first full-scale plutonium production reactor in the world. Plutonium manufactured at the site was used in the first nuclear bomb, tested at the Trinity site, and in Fat Man, the atomic bomb that was detonated over Nagasaki, Japan.
During the Cold War, the project expanded to include nine nuclear reactors and five large plutonium processing complexes, which produced plutonium for most of the more than 60,000 weapons built for the U.S. nuclear arsenal. Nuclear technology developed rapidly during this period, and Hanford scientists produced major technological achievements.