Series 13: Research Files contains numerous files of research on a variety of topics.

This series is predominately composed of research materials such as notes, articles and papers, interview transcripts, correspondence, and audiovisual media that were created or collected by Oberdorfer for various writing projects. Most of the materials pertain to Oberdorfer's biography of Senator Mike Mansfield or to Oberdorfer's interest in Korea, including some materials specifically related to his book The Two Koreas: A Contemporary History. Correspondence with Oberdorfer's publishers and promotional materials for these books are also present.