Lecture notes; student notebooks; manuscript materials; subject files; reprints; correspondence; sound recordings, miscellaneous materials. The lecture notes (1926-1962) are for courses given by Hoag at the University of Chicago, the University of Florida, and the Coast Guard Academy. Student notebooks (1917-1924) are from courses at Colorado College and the University of Chicago taught by Arthur J. Dempster, Albert A. Michelson, and Robert A. Millikan. The theses (1921-1927 and 1921-1939) are Hoag's undergraduate and Ph.D. theses, as well as those of his students at the University of Chicago. Manuscript materials (1928-1959) consist of drafts of books and articles on such subjects as electron and nuclear physics, history of Greek science, the scientific method, satellites, laboratory manuals, and artificial disintegration. The subject files consist of notes, reference notes, and typescripts on various topics: methodology, molecular physics, lectures and publications, etc. Reprints (1927-1948) are by Hoag, and reprints (1914-1963) are by colleagues on topics of spectroscopy, electron and nuclear physics, and ultra short wave radio. The correspondence (1929-1962) concerns apparatus, the Michelson Museum at China Lake, and two books by Hoag: ELECTRON PHYSICS and BASIC RADIO. Correspondents include: Adrian N. Clark, Edward M. Crane, Glenn M. Hobbs, Julian E. Mack, Robert A. Millikan, Thomas C. Poulter, and Morton H. Teller.