Manhattan Project

The Manhattan Project was a big research program during World War II. Its goal was to build the first nuclear weapons. The United States led it, with help from the United Kingdom and Canada. Many scientists, engineers, and military leaders worked together.

The project was led by Major General Leslie Groves from the U.S. Army Corps of Engineers. A scientist named J. Robert Oppenheimer led the Los Alamos Laboratory in New Mexico, where they designed the bombs. The project was named after Manhattan, where it started.

They made two types of atomic bombs: Little Boy and Fat Man. The first test of a nuclear bomb, called the Trinity test, happened on July 16, 1945, in New Mexico. Later, these bombs were used in Japan, which helped end World War II. The Manhattan Project also tried to learn about Germany’s nuclear work and faced some problems with people trying to steal secrets.

Origins

For a chronological guide, see Timeline of the Manhattan Project.

The discovery of nuclear fission in 1938 showed that an atomic bomb might be possible. Scientists worried that Germany might build one first. In 1939, a letter signed by Albert Einstein warned President Roosevelt about this danger. Roosevelt started a small group to study uranium.

When World War II began, Britain shared its atomic research with the United States. An Australian scientist named Mark Oliphant visited American labs and encouraged more scientists to work on the project. After the attack on Pearl Harbor, the United States joined the war, and the project became more important. Scientists looked at different ways to build reactors and prepare materials. The project grew fast as leaders wanted to act quickly.

Organization

Manhattan District

In June 1942, Major General Eugene Reybold chose Colonel James C. Marshall to lead part of the Manhattan Project. Marshall set up offices in New York City and worked with engineers and scientists. The project was first called “Development of Substitute Materials,” but it became known as the Manhattan District because much of the work happened there.

Later, Major General Leslie Groves took charge of the project. He asked J. Robert Oppenheimer to help design the atomic bomb. The United States worked with the United Kingdom and Canada, sharing ideas and help. This teamwork was important for building the first nuclear weapons during World War II.

Main article: British contribution to the Manhattan Project

Project sites

!Los Alamos Project Y

Los Alamos Project Y

!Alamogordo Trinity test

Alamogordo Trinity test

!RichlandHanford Engineer Works

Richland
Hanford Engineer Works

!Oak RidgeClinton Engineer Works

Oak Ridge
Clinton Engineer Works

!BerkeleyRadiation Laboratory

Berkeley
Radiation Laboratory

Metallurgical Laboratory

Chicago Metallurgical Laboratory

!Ames Project

Ames Project

!Dayton Project

Dayton Project

!Montreal Laboratory

Montreal Laboratory

!Chalk River Laboratories

Chalk River Laboratories

!Inyokern Project Camel

Inyokern Project Camel

!MonticelloVanadium Corp.

Monticello
Vanadium Corp.

!UravanUS Vanadium Corp.

Uravan
US Vanadium Corp.

!Wendover Project Alberta

Wendover Project Alberta

!TrailCominco

Trail
Cominco

!Wabash River Ordnance Works

Wabash River Ordnance Works

!Morgantown Ordnance Works

Morgantown Ordnance Works

!Alabama Ordnance Works

Alabama Ordnance Works

!ClevelandNational Carbon Company

Cleveland
National Carbon Company

!St LouisMallinckrodt

St Louis
Mallinckrodt

!RochesterMedical Section

Rochester
Medical Section

A selection of US and Canadian sites important to the Manhattan Project. Research and production took place at more than thirty sites across the US, the UK, and Canada. Click on the location for more information.

• Purple: Fissile material production
• Orange: Feed materials production
• Green: Research
• Black: Logistics/other

Oak Ridge

Main article: Clinton Engineer Works

The Manhattan Project needed a big place to make special materials. Oak Ridge in Tennessee was chosen and built quickly. Thousands of people moved there to help with the work. The town grew fast, and by 1945, it had over 75,000 people.

Los Alamos

Main article: Project Y

Los Alamos in New Mexico was chosen as a quiet place to design the first nuclear weapons. It was far away from cities, which made it safer. Scientists and workers lived there in a special community while they did their important work.

Chicago

Main article: Metallurgical Laboratory

Near Chicago, scientists built one of the first nuclear reactors. This was a big step in learning how to control nuclear reactions. The reactor was hidden under a big stadium to keep it safe.

Hanford

Main article: Hanford Engineer Works

Hanford in Washington was chosen to make special materials for the nuclear weapons. It was far from big cities, which made it safer. Thousands of people lived there while they built and worked in the factories.

Canadian sites

Main article: Montreal Laboratory

Canada helped with research and making special materials. Scientists from Canada worked with teams in the United States. Different places in Canada made important parts for the project.

Heavy water sites

Main article: P-9 Project

Some special factories were built in the United States to make heavy water, which was needed for certain types of nuclear reactors. These factories used different methods to produce heavy water.

Uranium

The Manhattan Project used uranium as an important material. Uranium helped make fuel for reactors, create plutonium, and build atomic bombs. In 1940, four main places had uranium: Colorado, northern Canada, Joachimsthal in Czechoslovakia, and the Belgian Congo. Most of these places were controlled by the Allies. By 1942, enough uranium was found for the project’s needs.

Uranium ore was changed into different forms for use. One way used nitric acid to make uranyl nitrate. This was then turned into uranium trioxide and uranium dioxide. Different methods were tried to separate uranium-235 from uranium-238. These methods included electromagnetic separation, gaseous diffusion, and thermal diffusion. Each method used special technology to enrich the uranium for bombs.

Plutonium

The Manhattan Project made two main types of nuclear weapons. One type used plutonium, a special material made in reactors. Uranium is changed into plutonium when it is hit with neutrons in a reactor. This creates plutonium-239, which can be taken out and used in weapons.

Important places were built to make and separate plutonium. The X-10 Graphite Reactor at Oak Ridge was an early test site. Bigger reactors were later built at Hanford. These reactors made the plutonium used in the first atomic bomb called "Fat Man." This bomb used a special design to create a big explosion.

Personnel

At its peak in June 1944, the Manhattan Project had about 129,000 workers. These included construction workers, plant operators, and military personnel. The project needed many highly skilled workers, which was hard to find because of other needs during the war.

The project included a few African-American scientists and technicians and had more women in technical roles than later government projects.

The Army helped provide skilled workers through programs like the Army Specialized Training Program and the Special Engineer Detachment. The Women's Army Corps (WAC) also helped, taking on technical and scientific tasks. The project's Medical Section, led by Stafford L. Warren, focused on health and safety for workers.

Secrecy

The Manhattan Project worked in secret during World War II. Only a few people knew about it, and everyone followed rules to keep it hidden. Workers sometimes did not know why they were doing their jobs. This helped keep the project safe from enemies.

The project had trouble staying secret because so many people were involved and there were worries about spying. But it stayed mostly hidden until the war ended.

Foreign intelligence

Main article: Alsos Mission

The Manhattan Project also tried to find out what other countries were doing to build atomic bombs. They were especially worried that Germany might be close to making its own weapon. To help stop this, they did bombings and sabotage at important factories in German-occupied Norway. A special team called the Alsos Mission was formed to look into scientific work in enemy countries. This team moved with the Allied armies across Europe, talking to scientists and searching places where such work might have happened.

The Alsos Mission found that Germany’s nuclear program had only done small experiments. They also took important materials and scientists from Germany to England for more study. This helped the Allies learn about Germany’s atomic research and made sure valuable resources did not fall into the hands of the Soviet Union.

Atomic bombings of Hiroshima and Nagasaki

Main article: Atomic bombings of Hiroshima and Nagasaki

The United States used the first atomic bombs near the end of World War II. Two cities in Japan, Hiroshima and Nagasaki, were chosen because they were important places for the war.

On August 6, 1945, an American plane dropped a bomb on Hiroshima. The explosion destroyed much of the city. Three days later, on August 9, another bomb was dropped on Nagasaki, and it also caused great destruction. These events helped Japan decide to surrender, ending World War II. The use of these bombs is still talked about by historians today.

After the war

After World War II, the Manhattan Project became well known for helping create the first nuclear weapons. The project officially ended on December 31, 1946, but its work kept influencing science and decisions. Scientists and leaders got awards for what they did, and the project helped start new ways to study and use nuclear energy.

The Manhattan Project had many challenges after the war, such as technical problems and changes in its team. Some places were closed, and new methods were created to make nuclear technology better. The project also took part in early nuclear tests, which showed how powerful these new weapons were. As the world thought about the future of nuclear science, many scientists asked for international control to avoid a dangerous competition for more weapons.

Cost

The Manhattan Project cost about $2 billion by the end of 1945, which is around $28 billion today. Most of the money was used to build factories for the materials needed for the atomic bombs. During the war, Congress was not told about the project to keep it secret, and the funds were hidden in other bills.

The project produced three atomic bombs, with the average cost per bomb being about $500 million in 1945 dollars. This made it the second most expensive weapons project for the United States during the war, only behind the Boeing B-29 Superfortress.

Legacy

See also: Nuclear weapons in popular culture

The Manhattan Project changed the world by creating nuclear weapons. The first nuclear tests showed how powerful these weapons were. This led many countries to develop their own nuclear technology.

The project helped create important research centers, like the Los Alamos National Laboratory and Oak Ridge National Laboratory. These labs now work on many big science projects and advanced computing. The work from the Manhattan Project also helped start new fields like nuclear medicine, which uses special materials to help diagnose and treat diseases. However, the project also caused some environmental problems that are still being cleaned up.

The Manhattan Project National Historical Park was established on 10 November 2015.