Incoming and outgoing letters, telegrams, and cards of both a business and personal nature. Correspondents include friends, colleagues, aspiring authors, editors and publishers, writers, university staff and faculty, literary and political organizations, students, and fans. Some letters are also to Muriel Cowley.

Types of correspondence include invitations to speak, solicitations for papers, requests for permission to quote and use works, recommendations by Cowley for former students and friends, business and travel arrangements, and commentary about publishing and social matters. The majority of Cowley's outgoing letters are carbon copies typed on scraps with fragments of his writings on the other side. Several folders contain correspondents' works, clippings, or photographs, as indicated.

For more correspondence, see also Series 2: Working Files, Series 3: American Academy Files, Series 4: Yaddo Files, Series 5: Kenneth Burke Files, Series 6: Family Papers, Series 7: Financial Files, and Series 8: Personal Files.