Correspondence, diaries, notebooks and notes, photographs. Materials documenting all aspects of Hale's life, including his role in the founding of Kenwood, Yerkes, Mount Wilson, and Palomar Observatories, California Institute of Technology, Huntington Library, National Research Council, American Astronomical Society, International Astronomical Union, Astrophysical Journal, etc. The collection contains significant amounts of correspondence with individuals including Charles G. Abbot, John Alfred Brashear, Edwin B. Frost, Robert A. Millikan, and with organizations including the International Research Council, National Academy of Sciences, Carnegie Institution of Washington, and the American Association for the Advancement of Science. Also included are notebooks, drafts of articles, correspondence concerning Hale's spectrohelioscope, diaries, family correspondence, biographical and autobiographical materials, condolences on Hale's death, and the director's files of Mount Wilson Observatory. Other correspondents include Giorgio Abetti, Albert Einstein, Henry Huntington, Hendrik Antoon Lorentz, Edwin B. Wilson, and Robert S. Woodward.