This series contains approximately 500 letters arranged alphabetically by correspondent. This is largely Elisabeth Gilman's incoming letters, but some outgoing letters to family members and a few friends are included. Letters to her parents in 1900 describe an ocean crossing and a stay in Italy. Gilman's letters to her sister Alice and her aunt Louise, 1917 to 1919 describe her service with the YMCA in France during World War I.

The incoming correspondence is less personal and reveals more of her life-long interest in social issues. Some of the letters are concerned with fund raising for organizations with which she affiliated, and others deal with arrangements for problem-solving programs. Correspondence with James G.P. Stokes in 1917 establishes Gilman's religious inspiration for Socialism. Other public figures of this period who shared Gilman's political persuasion are represented including Norman Thomas, Scott Nearing, Vida Scudder, John Dewey, Jane Addams, and Edward Keating. Correspondence with the American Friends Service Committee, the American Association for Old Age Security, and the Baltimore Urban League indicate support for her political campaigns.

In the mid-1930s, Gilman sought a biographer to chronicle her father's life and work at The Johns Hopkins University. Letters of H.M. Kallen indicate that several authors were considered. A letter of John Dewey, July 5, 1935, included with Kallen's letters indicates his (Dewey's) interest in the matter. It was Abraham Flexner who eventually undertook the project, and his letters are part of this series. Dr. William H. Howell corresponded with Gilman regarding the biography, and his personal reminiscences of Daniel C. Gilman are included in the Personal Series.