Hanford is a mostly decommissioned nuclear production complex on the Columbia River in Washington, operated by the U.S. government. Established in 1943 as part of the Manhattan Project, plutonium manufactured at the site was used in the first nuclear bomb. The weapons production reactors were decommissioned at the end of the Cold War, but the decades of manufacturing left behind 53 million gallons of high-level radioactive waste, 25 million cubic feet of solid radioactive waste, 200 square miles of contaminated groundwater beneath the site and occasional discoveries of contaminations. The Hanford site represents two-thirds of the nation’s high-level radioactive waste by volume. Today, Hanford is the most contaminated nuclear site in the United States and is the focus of the nation’s largest environmental cleanup.