<P> The Manhattan Project was a research and development project that produced the first atomic bombs during World War II . It was led by the United States with the support of the United Kingdom and Canada . From 1942 to 1946 , the project was under the direction of Major General Leslie Groves of the US Army Corps of Engineers . The Army component of the project was designated the Manhattan District ; `` Manhattan '' gradually became the codename for the entire project . Along the way , the project absorbed its earlier British counterpart , Tube Alloys . The Manhattan Project began modestly in 1939 , but grew to employ more than 130,000 people and cost nearly US $2 billion ( about $27 billion in 2017 dollars ) . Over 90 % of the cost was for building factories and producing the fissionable materials , with less than 10 % for development and production of the weapons . </P>
<P> The Manhattan Project was a research and development project that produced the first atomic bombs during World War II . It was led by the United States with the support of the United Kingdom and Canada . From 1942 to 1946 , the project was under the direction of Major General Leslie Groves of the US Army Corps of Engineers . The Army component of the project was designated the Manhattan District ; `` Manhattan '' gradually became the codename for the entire project . Along the way , the project absorbed its earlier British counterpart , Tube Alloys . The Manhattan Project began modestly in 1939 , but grew to employ more than 130,000 people and cost nearly US $2 billion ( about $27 billion in 2017 dollars ) . Over 90 % of the cost was for building factories and producing the fissionable materials , with less than 10 % for development and production of the weapons . </P>
when did the manhattan project began and end
when did the manhattan project began and end
From 1942 to 1946
From 1942 to 1946