1942 - 1953

  • Roosevelt approves production of the atomic bomb

    President Roosevelt approves production of the atomic bomb following receipt of a National Academy of Sciences report determining that a bomb is feasible.
  • Executive Order 9066 is signed

    President Franklin D. Roosevelt signs executive order 9066 allowing the United States military to define areas as exclusionary zones.
  • The Army Corps of Engineers establishes the Manhattan Engineer District to develop and build the atomic bomb

    The Army Corps of Engineers establishes the Manhattan Engineer District to develop and build the atomic bomb. Uranium isotope separation facilities are built at Oak Ridge, Tennessee; plutonium production reactors are built at Hanford, Washington; and a weapons laboratory is set up at Los Alamos, New Mexico.
  • Manhattan Project

    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
  • The G.I. Bill of Rights

    The G.I. Bill of Rights is signed into law, providing benefits to veterans.
  • President Roosevelt dies

    President Roosevelt dies suddenly; Vice President Harry S. Truman assumes the presidency and role as commander in chief of World War II.
  • Use of Atomic Bomb

    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.
  • United States Enters the United Nations

    United States Senate approves the entry of the United States into the United Nations.
  • National Security Act of 1947

    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.
  • Marshall Plan

    On April, 3rd 1948 President Harry Truman signs the Marshall Plan, which authorizes $15 billion in aid for 16 countries.
  • Korean War Begins

  • Korean War Ends