The first months on the mesa required drastic adjustments – to Oppenheimer's style of scientific leadership, to Groves's close administration of the town, and to the unusual partnership between scientists and the military. The laboratory grew more rapidly than anticipated because in the early months of the project Oppenheimer and Warren K. Lewis's advisory committee recognized that a scientific community of some 100 scientists was too small to cope with the complexities of producing an atomic bomb. Broadening the laboratory mission, as the Lewis Committee recommended, implied the absorption of new sub communities, including the Army Special Engineer Detachment (SED) and the British Mission.

Life in wartime Los Alamos was abnormal in almost every respect, but the townspeople strived toward normalcy in their everyday lives, meeting their practical concerns about food, shelter, amusement, and schools with a spirit of adventure. The spartan simplicity and transience of housing and the lack of many community services often turned daily life into a struggle. But as Kathleen Mark reflected, “When one considers that we lived … closely packed together – aware of every detail of our neighbor's lives – even to what they were having for dinner every night – one can't help but marvel that we enjoyed each other so much.” The residents worked and also played hard in the isolated military community to which they were restricted.