The Manhattan Project and Creation of American Atomic Bombs

Soon after the 2 billion dollar funding was approved on December 6th, 1941, the top secret Manhattan Project was developed in 9 states and was devoted to creating an atomic bomb for possible use in WWII.  This project was created on an enormous scale in order to speed up the process of development, and employed over 100,000 people.  Originally two very large plants were constructed to deal with atoms of very heavy elements.  One of these plants was created for separating U-235 atoms (Uranium), and the other for producing Pu-239 (Plutonium.)  This project was given to the US Army Crops of Engineers, and was run by General Leslie R. Groves.  It took about three years to produce a bomb that could be tested.  Even before a bomb could be tested, a separate bomb was being shipped across the pacific for possible use on Japan.  
Manhattan Project Activity Centers
The Manhattan project was proven to be a success when the first atomic bomb to ever be detonated on earth was tested at the site Trinity in Alamogordo, New Mexico on July 16th, 1945.  Some of scientists involved in the project feared that a explosion the size of the one expected from the plutonium bomb would cause a cataclysmic reaction in the upper atmosphere and cause the destruction of the earth.  At the very least people feared for the communities surrounding the site because of the possible nuclear fallout.  These doubts were ignored because it was assumed that another nation given the chance would test one of the bombs, and that the project would produce bombs we could use. The test was a great success, and produced an explosion equal to that would be produced by about 20,000 tons of TNT.  The explosion completely vaporized the 100 foot observation tower it was attached to, and instantly fused the surrounding desert sand to glass.  
"The Atomic Age began at exactly 5:30 Mountain War Time on the morning of July 15, 1945, on a stretch of semi-desert land about 5 airline miles from Alamogordo, New Mexico."And just at that instance there rose from the bowels of the earth a light not of this world, the light of many suns in one."

William Laurence
New York Times
September 26, 1945