What was it like to live at Los Alamos during the Manhattan Project? As thousands worked to build a top-secret atomic device, the US military tried to keep the entire city secret. All mail was screened and sent through a fake address at the University of California. The security team warned residents to never use their real names, and to cancel all their magazine subscriptions. And the FBI even investigated the head librarian, suspecting that she was sharing secrets with the communists.