The Professional Correspondence series consists mainly of Hayden's file of correspondence, personal and professional. Because of the importance of Hayden's correspondents, a selective index to these letters has been prepared and is appended to this finding aid. The researcher should note that there is other correspondence that forms parts of other series. The researcher is directed to those files maintained by Lloyd Millegan and Olivia Hayden, described below.
Arranged topically, the Philippine collection series includes the following subseries: Administrative; Economic; Education; Foreign Relations; Historical and Social; Legislative, Constitutional and Judicial; Political; Provincial; and Miscellaneous. Within each of these subseries, there are further subdivisions made clear by the folder listing. The arrangement of the Philippine Collection is in much the same order as that developed and maintained by Hayden. Types of materials found within the various folders include reports and memoranda, both official and informal, addresses and speeches, documents of an official nature (such as copies of legislation, budgets, departmental reports, and minutes of meetings), correspondence, and clippings. The Philippine Collection includes photographs that Hayden collected while serving in the Philippines. Also in this series are four motion pictures (with VHS use copies) of scenes of Filipinos life and the Philippine countryside, government installations, American personnel, and official daily life in the Philippine Islands during the mid-1930s.