The Project

Concerned that Nazi scientists were creating a bomb capable of horrific destruction, the U.S. government launched the Manhattan Project to develop an atomic bomb before the Germans could. They tasked the best scientists and engineers available to harness the power of the atom, creating the atomic bomb.

The Manhattan Project consisted of three main sites: Oak Ridge, Tennessee; Hanford, Washington; and Los Alamos, New Mexico. Oak Ridge was responsible for the enrichment of uranium, U-235, which ultimately fueled the atomic bomb “Little Boy.” The site at Hanford created plutonium, which was used to create the atomic bomb “Fat Man.” Scientists and engineers developed weapon technology to use these enriched nuclear materials at Los Alamos.

On August 6, 1945, the U.S. dropped Little Boy on the Japanese city of Hiroshima and three days later dropped Fat Man on Nagasaki, Japan.

Between the three locations, the Manhattan Project cost more than $2 billion, equivalent to roughly $26 billion in 2015 dollars, and employed more than 130,000 men and women.

The Purpose

While the government launched the Manhattan Project to develop atomic weapons that would put an end to World War II, the project also became a catalyst for extraordinary advances in a variety of fields including medicine, power generation, and space exploration.

The park is not intended to celebrate the atomic bomb; rather, its purpose is to preserve the legacies and histories of people, events, science, and engineering that changed the world forever.

August, 1939

A letter to the President
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December, 1941

The Japanese attack Pearl Harbor
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September, 1942

"Site X" is approved in East Tennessee
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November, 1942

"Site Y" is designated in Los Alamos, New Mexico
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January, 1943

"Site W" is chosen in southern Washington
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February, 1943

X-10 reactor and Y-12 plant
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April, 1943

Bomb design begins at Los Alamos site.
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July, 1943

Manhattan Project sites proclaimed military districts
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November, 1943

X-10 reactor in Oak Ridge reaches criticality
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February, 1944

First enriched U-235 is delivered to Los Alamos
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September, 1944

Hanford's Reactor B goes critical
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February, 1945

Hanford delivers plutonium-239 to Los Alamos
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May, 1945

European theater of WW2 ends
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July, 1945

Test device detonated near Alamogordo, NM
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August, 1945

Atomic bombs are dropped on Japan
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September, 1945

Japan surrenders to the Allies
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January, 1948

Atomic Energy Act goes into effect
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November, 2015

Establishment of Manhattan Project National Historical Park
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