Roger Hildebrand is an American physicist and the S.K. Allison Distinguished Service Professor, Emeritus, at the University of Chicago. His involvement with the Manhattan Project began with a tap on the shoulder by Ernest Lawrence, who convinced Hildebrand to shift from being a chemist to a physicist. He worked with cyclotrons and mass spectrometers at Berkeley before transferring to the Y-12 Plant in Oak Ridge. In this interview, Hildebrand shares his memories of Lawrence, Enrico Fermi, Samuel Allison, and other Manhattan Project scientists. He recalls his postwar work at the University of Chicago, and the pressure he felt after being asked to be a substitute in one of Fermi’s classes.