Science1942–1946

The Manhattan Project

Also called: Manhattan Engineer District

The secret programme in which the United States, with Britain and Canada, built the atomic bomb. Under General Groves from 1942 it raised secret cities at Oak Ridge, Hanford and Los Alamos, employing over 130,000 people at a cost of some $2 billion.

Operators watching the uranium-enrichment calutrons at the Y-12 plant, Oak Ridge, 1944 — most did not know what they were making
doe-oakridge · Public domain · Source

When Pearl Harbor brought the United States into the war in December 1941, atomic research became a military project. Named the Manhattan Engineer District after its first office in Manhattan, New York, it was placed in September 1942 under General Leslie Groves, who had overseen the building of the Pentagon. British and Canadian scientists joined it.

To make the bomb’s material, a vast plant to enrich uranium-235 rose at Oak Ridge, Tennessee, and reactors to make plutonium at Hanford, Washington, while at Los Alamos, New Mexico, scientists under Oppenheimer designed the bomb itself. More than 130,000 people worked on it, most without knowing what they were building, at a cost of about $2 billion in the money of the day. The Soviet Union stole its secrets through spies such as Klaus Fuchs.

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States and rulers at the time: United States · led by — President Franklin D. Roosevelt
Places: Oak Ridge, Hanford Site, Los Alamos

People

Leslie Groves1896 – 1970
commander · US Army general who oversaw the building of the Pentagon and from 1942 commanded the whole Manhattan Project
J. Robert Oppenheimer1904 – 1967
key figure · American physicist who directed the Los Alamos laboratory and led the building of the atomic bomb — the "father of the atomic bomb" — and after the war opposed the hydrogen bomb
Franklin D. Roosevelt1882 – 1945
related figure · 32nd US president (1933–1945) who led the New Deal and took the US to war after Pearl Harbor; he attended the Cairo and Yalta conferences

3 parts of this event

1
1942Chicago Pile-1 — The First Chain Reaction
On 2 December 1942, in the world’s first reactor — graphite and uranium stacked by Enrico Fermi beneath the stands of the University of Chicago’s football field — a man-made nuclear chain reaction sustained itself for the first time.
2
1943The Los Alamos Laboratory
In 1943 a secret laboratory to design the atomic bomb was founded on a remote mesa at Los Alamos, New Mexico. Oppenheimer, its director, gathered leading scientists including Fermi and Bohr.
3
1945The Trinity Test
Before dawn on 16 July 1945 the world’s first atomic bomb was tested successfully in the New Mexico desert. The mushroom cloud rose 12 kilometres, and Oppenheimer recalled a line from Hindu scripture: "Now I am become Death, the destroyer of worlds."

Before and after

Earlier: 1939 World War II
Later: 1943 Cairo Declaration

Themes that include this event

The Birth of the Atomic Bomb1938 – 1949
From the discovery of fission to the first Soviet bomb — Einstein’s letter, the Manhattan Project, the Trinity test, Hiroshima and Nagasaki, and the dawn of the nuclear age