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This section provides an overview of the history of the Manhattan Project, the key organizations involved, the science behind the bomb, and more.

British Nuclear Program

The story of U.S.-U.K. nuclear partnership is one of both collaboration and division.
U.S. and Spanish officials with the recovered fourth bomb after the Palomares incident.

Broken Arrow Accidents

The U.S. military uses the term “Broken Arrow” to refer to an accident that involves nuclear weapons or nuclear weapons components.
The B Reactor at Hanford

Building the Bomb - 1943

The most difficult part of the Manhattan Project was not the scientific theory of the bomb but the engineering.
Doomsday Clock

Bulletin of the Atomic Scientists

The Bulletin of the Atomic Scientists is a journal founded in 1945 that analyzes nuclear policy challenges.
PM-2 nuclear reactor at Camp Century

Camp Century

During the Cold War, the U.S. Army built a military complex under the Greenland ice sheet as a prototype for nuclear missile silos.
Castle Bravo. Image courtesy of Los Alamos National Laboratory.

Castle Bravo

On March 1, 1954, the United States carried out its largest nuclear detonation, “Castle Bravo,” at Bikini Atoll in the Marshall Islands. The Bravo explosion was more than two and a half times greater than expected and caused far higher levels of fallout and damage than scientists had predicted.
Graphite blocks arranged in the same manner as CP-1

Chicago Pile-1

On December 2, 1942, Chicago Pile-1 went critical, creating the world’s first controlled, self-sustaining nuclear chain reaction.
A model of the first Chinese atomic bomb

Chinese Nuclear Program

In 1964, China became the fifth country to possess nuclear weapons.
US Government's No Trespassing Sign on Hanford Land

Civilian Displacement: Hanford, WA

Before the Manhattan Project, about two thousand people lived in White Bluffs, Hanford, and Richland, WA or nearby. For centuries, four different Native American tribes enjoyed the land along Columbia River.