Short answers, pulled from the story.
Major General Leslie Groves officially created the Manhattan District on the 13th of August 1942. This Army engineering unit was established to oversee the most expensive and secretive project in human history.
James Chadwick discovered the neutron in the early 1930s. Leo Szilard patented the process of using neutrons to release energy in a nuclear chain reaction in 1934.
United States Under Secretary of War Robert P. Patterson authorized the Corps of Engineers to acquire 57,000 acres of land on the 29th of September 1942. The order came into effect on the 7th of October 1942, affecting about 1,000 families.
The first nuclear device ever detonated was an implosion-type bomb during the Trinity test on the 16th of July 1945. This test took place at White Sands Proving Ground in New Mexico.
The Little Boy bomb was dropped on Hiroshima on the 6th of August 1945. The Fat Man bomb was dropped on Nagasaki on the 9th of August 1945.
The United States Atomic Energy Commission formed in January 1947. This body took over control of American atomic weapons research and production from the Manhattan Project.