Chicago Pile One (CP-1)
Construction of CP-1, or Chicago Pile Number One, was done under the football stadium in an abandoned squash court. On December 2, 1942, mankind first harnessed the energy of the atom. Fermi's pile produced only 1/2 watts of power. But that was all the power the United States needed to start the next phase of the bomb's development.
The pile contained 771,000 pounds of graphite, 80,590 pounds of uranium oxide and 12,400 pounds of uranium metal when it went "critical." It cost about $1 million to produce and build. The pile took the form of a flattened ellipsoid which measured 25 feet wide and 20 feet high.