This collection of correspondence, manuscripts, and copies of documents pertains to Powell's unpublished biography of John Dickinson ("John Dickinson, Penman of the American Revolution," 1938). There are letters to numerous historians, and many articles and speeches that Powell gave.

This collection consists primarily of correpondence and writings by Murphy. The correspondence is both family and professional, the former being largely of a social nature and including letters of her grandfather (Amos Chafee Barstow), mother (Grace P. Barstow), and sister (Mary Mason Barstow). Much of the correspondence with her sister reveals Murphy's interest in, and dedication to, conservation. There are articles and speeches pertaining to her interest in conservation or relating to the various trips she took with her husband, Robert Cushman Murphy.

These documents cover the years 1847 to 1953, the year of Millikan's death, but the core of the collection consists of the official papers generated by Millikan after his move to Pasadena in 1921. The collection includes more than 125,000 pages of letters, notebooks, unpublished speeches, addresses, lecture notes, and family papers.