Correspondence, journals, writings, reviews, speeches, research notes, interviews, reports, transcripts of hearings, newspaper clippings, printed materials, and other papers pertaining to Lattimore's studies in Chinese and Mongolian history and linguistics, his appointment by President Franklin D. Roosevelt as a political advisor to Chiang Kai-shek, and his service as director of Pacific Operations in the U.S. Office of War Information Overseas Operations Branch during World War II, the war against Japan and American assistance in the Chinese war effort, Lattimore's postwar work as a member of the U.S. Reparations Mission to Japan, Senator Joseph R. McCarthy's accusations that Lattimore was a communist and Soviet agent and subsequent Senate Foreign Relations Committee investigations (1951), and the establishment of the Lattimore Institute for Mongolian Studies. Includes papers (1924-1970) of his wife, Eleanor Holgate Lattimore (1895-1970).

Correspondents include Joseph Barnes, Robert LeMoyne Barrett, Arnold Bernhard, Stanley H. Burton, Rosemary Carruthers, Isabel Casseres, G. Herbert Childs, Lauchlin Bernard Currie, Ildikó Ecsedy, John King Fairbank, Diluv Khutagt, Else Glahn, Elvebeuck Grebenik, Walther Heissig, Caroline Humphrey, Fujiko Isono, Joseph Needham, John Ulric Nef, Robert P. Newman, Urgunge Onon, Gerard Piel, Margaret L. Richards, Edgar Snow, Vilhjalmur Stefansson, and Arnold Joseph Toynbee.