Timeline of The Manhattan Project - 1943

1943

• January 16: Groves approves development of the Hanford Site.
• February 9: Patterson approves acquisition of 400,000 acres (160,000 ha) at Hanford.
• February 18: Construction begins for Y-12, a massive electromagnetic separation plant for enriching uranium at Oak Ridge.
• April 1: Los Alamos laboratory is established.
• April 5–14: Robert Serber delivers introductory lectures at Los Alamos, later are compiled into The Los Alamos Primer.
• April 20: The University of California becomes the formal business manager of the Los Alamos laboratory.
• June 2: Construction begins of K-25, the gaseous diffusion plant.
• July 10: First sample of plutonium arrives at Los Alamos.
• August 13: First drop test of gun-type fission weapon at Dahlgren Proving Ground under the direction of Norman F. Ramsey.
• August 13: Kenneth Nichols replaces Marshall as head of the Manhattan Engineer District. One of his first tasks as district engineer is to move the district headquarters to Oak Ridge, although its name did not change.
• August 19: Roosevelt and Winston Churchill sign Quebec Agreement.
• September 8: First meeting of the Combined Policy Committee, established by the Quebec Agreement to coordinate the efforts of the United States, United Kingdom and Canada. United States Secretary of War Henry Stimson, Bush and Conant are the American members; Field Marshal Sir John Dill and Colonel J. J. Llewellin are the British members, and C. D. Howe is the Canadian member.
• October 10: Construction begins for the first reactor at Hanford Site.
• November 4: X-10 Graphite Reactor goes critical at Oak Ridge.
• December 3: The British Mission, 15 scientists including Rudolf Peierls, Otto Hahn, Franz Simon and Klaus Fuchs, arrives at Newport News, Virginia.