In September of 1942 Brigadier General Leslie Groves was selected to take command of the Manhattan Project. The goal of the project was to develop several industrial sites for the manufacturing of plutonium and uranium. In December 1942 a feasibility study on potential sites for these reactors identified Hanford as an ideal location. The site was subsequently named "Site W," the federal government acquired neighboring land and local residents were relocated away from the site.

Construction begins on the Hanford Engineer Works in March 1943. At its peak in 1944, more than 40,000 workers were employed at "Site W." With the scale of the project came a new town, dubbed Richland Village, where workers and their families lived in more than 4,000 family units and dormitories.

Construction began in July 1943 on the B Reactor, which at the time of its completion was the largest nuclear reactor ever built.

In September 1944 B Reactor achieved initial criticality, the first step in manufacturing plutonium for an atomic bomb.

Robert Oppenheimer, the director of the Los Alamos Laboratory conducts the first detonation of a nuclear weapon on the Alamagordo Bombing and Gunnery Range, now known as White Sands Missile Range, on July 17, 1945. The weapon, which included plutonium from Hanford's B Reactor, was a success, with a yield of 20 kilotons of TNT. The test was code named Trinity by Oppenheimer.

On August 9, 1945, a B-29 nicknamed "Bock's Car" and piloted by Major Charles Sweeney dropped an atomic bomb on the Japanese town of Nagasaki. The bomb, nicknamed Fat Man, was the second of the two bombs used but was the only one of the two that had plutonium provided by Hanford's B Reactor. The bomb had the force of 21 kilotons of TNT. Following the bombing of Hiroshima on August 6 and Nagasaki on August 9, the Japanese surrendered on August 12, 1945.

Hanford's B Reactor was briefly deactivated between 1946 and 1948. By 1949 it was back online, now producing tritium for hydrogen bombs.

Hanford suffered a criticality accident on April 7, 1962 at the plutonium processing plant. Criticality alarms were triggered due to an accident that included a plutonium solution spill. The building was evacuated and three people suffered significant radiation exposure.

The Atomic Energy Commission directs the shutdown of B Reactor. In 1976 it was declared a National Historic Engineering Landmark; in 2008 it was declared a National Historic Landmark. By 2009 public tours are announced by the Department of Energy and in 2011 the National Park Service recommends B Reactor be included in a Manhattan Project national historic park.

In September 1976 particles of radioactive material and glass flew into this room on the Hanford Nuclear Reservation in Richland, Wash. in 1976, injuring worker Harold McCluskey and exposing nine others to radioactivity. The space, now dubbed the McCluskey Room, is located inside the closed Plutonium Finishing Plant. McCluskey survived the incident and was dubbed the "Atomic Man." He lived for 11 years after the accident and died from causes unrelated to the accident.

The federal judge handling the huge Hanford downwinders’ lawsuit is keeping secret a report that sharply criticizes a $27 million, taxpayer-funded study of past radiation releases from the nuclear reservation. The study is flawed and may underestimate radiation doses to people living near Hanford, according to the courtappointed scientist who wrote the critique.

Taxpayers have shelled out $43 million so far in legal costs for the massive Hanford downwinders’ case, a legacy of Cold War radiation releases. About $35.8 million of the total has gone to lawyers defending five corporations who ran Hanford for the government from 1944 through 1986.

On May 14, 1997 a chemical tank exploded in the Plutonium Reclamation Facility. The reclamation facility is part of the Plutonium Finishing Plant, which produced plutonium powder, ultimately for nuclear warheads. About 10.7 tons of plutonium still are at the plant, about 150 feet away from the explosion. The plant, which has a long history of accidents and explosions, stopped production in 1989.

Deborah Clark, who was among those suing Hanford contractors over her cancer, has died. Clark, 61, passed away today of complications from thyroid cancer at a hospice in Longview, Wash.

Shannon Rhodes’ losing battle to prove that Hanford radiation emissions caused her spreading thyroid cancer spanned two trials and ended in federal court six years ago. Now, her life has ended as well – cut short by complications from metastasized thyroid cancer. Rhodes, a Coeur d’Alene artist and writer, died May 15 at her winter home in Green Valley, Ariz. She was 69.

The U.S. Department of Energy has tentatively agreed to settle the claims of 139 people with thyroid disease – the largest settlement so far in a massive civil suit brought by people exposed as children to clouds of radioactive iodine from Hanford during World War II and the early years of the Cold War.

Governor Jay Inslee announced in February 2013 that a radioactive waste storage tank had been leaking between 150 and gallons of liquids per year. Later in the month he added that six more tanks at Hanford had been identified as leaking liquids.

A report released Wednesday, Nov. 16, 2016, found that seven of 52 workers interviewed were worried about fear of retaliation related to raising concerns about exposure to chemical vapors escaping from nuclear waste storage tanks.

A portion of a storage tunnel that contains rail cars full of radioactive waste collapsed Tuesday morning, May 9, 2017, forcing an emergency declaration at the Hanford Nuclear Reservation in southeastern Washington.