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President Franklin D. Roosevelt signs executive order 9066 allowing the United States military to define areas as exclusionary zones. These zones affect the Japanese on the West Coast, and Germans and Italians primarily on the East Coast.
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June 20, 1942 - The development of the first atomic bomb is signed into agreement between the Prime Minister of Great Britain, Winston Churchill, and President Franklin D. Roosevelt in Hyde Park, New York.
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December 2, 1942 - The first nuclear chain reaction is produced at the University of Chicago in the Manhattan Project, creating fission of the Uranium U-235, under the direction of physicists Arthur Compton and Enrico Fermi.
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On January, 15 1943 the world's largest office building, The Pentagon, is dedicated in Arlington, Virginia.
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April 13, 1943 - The Jefferson Memorial in Washington, D.C. is dedicated on the 200th anniversary of Thomas Jefferson's birth by President Franklin D. Roosevelt.
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On January, 4 1944 Ralph Bunche appointed 1st African American official in US State Department.
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June 22, 1944 The G.I. Bill of Rights is signed into law, providing benefits to veterans.
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January, 20 1945 Franklin D. Roosevelt sworn-in for an unprecedented 4th term as US President.
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February 4-11, 1945. President Roosevelt, Prime Minister Churchill, and Premier Josef Stalin hold the Yalta Conference in the Soviet Union.
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On April 12, 1945 President Roosevelt dies suddenly; Vice President Harry S. Truman assumes the presidency and role as commander in chief of World War II.
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August 6, 1945 President Harry S. Truman gives the go-ahead for the use of the atomic bomb with the bombing of Hiroshima. Three days later, the second bomb is dropped on Nagasaki, Japan.
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December 4. By a vote of 65–7, the United States Senate approves the entry of the United States into the United Nations.
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December 5 of 1946 President Harry Truman establishes the President's Committee on Civil Rights to investigate the status of civil rights in the United States and propose measures to strengthen and protect the civil rights of American citizens.
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July 26 Cold War: U.S. President Harry S. Truman signs the National Security Act of 1947 into law, creating the Central Intelligence Agency, the Department of Defense, the Joint Chiefs of Staff, and the National Security Council.
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On April, 3rd 1948 President Harry Truman signs the Marshall Plan, which authorizes $15 billion in aid for 16 countries.
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January 31, 1950 President Harry S. Truman orders the development of the hydrogen bomb, in response to the detonation of the Soviet Union's first atomic bomb in 1949.
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February 27 1951 The Twenty-second Amendment to the United States Constitution, limiting Presidents to two terms, is ratified.
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December 31 1951. The Marshall Plan expires after distributing more than $13.3 billion USD in foreign aid to rebuild Europe.
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June 14 1952 the keel is laid for the U.S. nuclear submarine USS Nautilus.
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On January 7 1953 President Harry S. Truman announces the United States has developed a hydrogen bomb.
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Dwight D. Eisenhower(R) is sworn in as the 34th President of the United States.
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May 25 1953, Nuclear testing at the Nevada Test Site, United States conducts its first and only nuclear artillery test.
