Frank Walker's correspondence files begin in 1924 with his work in New York as general counsel to Comerford Amusement Enterprises and continue on to document his work with the Democratic Party, his positions within the Roosevelt administration, and his interests and activities after his retirement in 1952. The files are made up of fourteen separate alphabetical runs, each covering several years, and a group of subject files, set aside by Walker, consisting primarily of correspondence with and about Franklin Roosevelt and Harry Truman. Routine correspondence such as invitations, greeting cards, and congratulatory letters have also been filed in this series.

Correspondents include politicians, job seekers, White House and other government workers, New Deal officials in Washington and around the country, lobbyists, theater owners and others involved in the movie business, members of the Catholic hierarchy, administrators of the University of Notre Dame, and family and friends. Subjects discussed include political fundraising, Democratic Party conventions and campaigns, patronage jobs, New Deal policies and programs, the theater business, the finances, personnel, and procedures of the U.S. Postal Service, local affairs in Walker's hometown of Butte, Montana, and other personal matters. Correspondence with Roosevelt and Truman appears in both the general and the subject correspondence; the subjects covered in these letters include the presidents' speeches, messages that Walker had been asked to pass on to the White House, political strategy, and patronage matters.

The content and arrangement of Walker's correspondence reflects the fact that he was usually holding more than one job at a time. His official positions included Democratic Party treasurer (1932), director of the National Emergency Council in the Roosevelt administration (1933-1935), postmaster general (1940-1945), and chairman of the Democratic Party (1943-1944). But in addition to these jobs he was very active in Democratic Party affairs and the Roosevelt administrations throughout his career even during those years when he had no official duties. His correspondence is a source of information on these continuing interests as well as his official positions. Walker kept separate files for his work with the Democratic Party, the NEC, the Post Office, and his family business. These records can be found in other series in the Walker Papers, but much of the correspondence from these activities was filed with his general correspondence.