This collection shows photographs shows the construction of CP-1, or Chicago Pile Number One, that was done under the football stadium in an abandoned squash court at the University of Chicago. The pile contained 771,000 lbs. of graphite, 80,590 lbs. of uranium oxide and 12,400 lbs. 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 ft. wide and 20 ft. high.