By October 1942, the Metallurgical Laboratory had to consider how it would proceed with designing large production reactors when they had yet to get an experimental reactor to work. Fermi favored taking small steps, while Allison and Eugene Wigner argued that larger steps were necessary if atomic bombs were to be developed in time to affect the course of the war. The Director of the Manhattan Project, Brigadier General Leslie R. Groves, Jr., told them that time was more important than money, and if two approaches looked promising, they should build both. In the end, this was what was done. Allison was one of 49 scientists who watched the project take a leap forward when Chicago Pile-1 went critical at Stagg Field on December 2, 1942. As Compton's reactor project began to spread outside Chicago in 1943, Allison became director of the Metallurgical Laboratory in June 1943.