1943 - The federal government chooses Hanford to make plutonium for the Manhattan Project, the secret wartime effort to build an atomic bomb.
1943 - 30,713 employees
September 1944 - B Reactor, the world’s first production reactor, is turned on.
August 1945 - The “Fat Man,” a bomb made with Hanford plutonium, is dropped on Nagasaki, three days after the bombing of Hiroshima. The Japanese surrender six days later.
Dec. 2, 1949 - The U.S. Air Force intentionally releases a large amount of radiation over Eastern Washington as part of an experiment. There are no public warnings.
1950s - The government builds more reactors to increase plutonium production. Some of the reactors dump radioactive water into the Columbia River.
1963 - N Reactor is built to produce both plutonium and electricity.
1971 - The government announces N Reactor will close, but keeps it open after heavy lobbying from the TriCities and the Northwest congressional delegation.
1981 - President Ronald Reagan announces $180 billion arms buildup, triggering a race in the coming decade to produce more plutonium.
1986 - Hanford managers release declassified documents revealing for first time Hanford’s radioactive contamination of eastern Washington in ‘40s and ‘50s.
1988 - N Reactor is shut down and Hanford’s military mission ends.
1989 - Washington state, the Department of Energy and the U.S. Environmental Protection Agency sign an agreement to clean up Hanford’s radioactive mess.
1991 - The Cold War ends with collapse of Soviet Union.
1993 - Energy Secretary Hazel O’Leary pledges a new “openness” for the DOE and vows to reform operations at the nation’s weapons plants, including Hanford.
1994 - Hanford’s cleanup budget reaches $2 billion.
1994 - 18,760 employees