The B Reactor at the Hanford Site in Benton County, Washington, holds exceptional national significance as the world's first full-scale plutonium production reactor. Constructed during World War II as a critical component of the top-secret Manhattan Project, the reactor was built in an astonishingly brief period between 1943 and 1944 by the DuPont Company, utilizing experimental designs pioneered by Enrico Fermi and his team. The facility was designed to produce plutonium-239, a fissile isotope previously only created in microscopic laboratory quantities. The plutonium manufactured in the B Reactor core was used to fuel the "Gadget" detonated at the Trinity test in New Mexico-the world's first nuclear explosion-as well as the "Fat Man" atomic bomb dropped on Nagasaki, Japan, on August 9, 1945, which precipitously brought about the end of World War II.

As an engineering and scientific marvel of the twentieth century, the B Reactor represents a pivotal leap into the Atomic Age. The massive, graphite-moderated, water-cooled reactor proved the feasibility of large-scale nuclear transmutation and established technological precedents that guided both military and civilian nuclear development for decades. Beyond its technological achievements, the site stands as a physical testament to the unprecedented mobilization of wartime labor, resources, and scientific intellect. Designated a National Historic Landmark in 2008 and now preserved as a premier unit of the Manhattan Project National Historical Park, the B Reactor remains an unparalleled monument to the dawn of nuclear weapons, the Cold War, and modern global geopolitics.