The Selected Correspondence and Related Materials series contains Eberstadt's professional correspondence with government officials, politicians, and academics, as well as businessmen and investment bankers, policy organizations, social clubs, and charity groups. The series also includes correspondence that Eberstadt was copied on, and related government reports, records of Congressional hearings, meeting minutes, memoranda, academic papers, pamphlets, newspaper clippings, and photographs. The majority of the correspondence is related to Eberstadt's service to the United States government on defense and economic issues, especially during the 1940s and 1950s, including with the Reparations Conference in Paris in 1929, the Army-Navy Munitions Board, the War Production Board, with armed services unification and Defense Department reorganization, the Atomic Energy Commission, and the Hoover Commission on Government Reorganization. Significant correspondents include Bernard M. Baruch, James V. Forrestal, and Herbert Hoover. The correspondence documents Eberstadt's service to these organizations and their work with World War II policies, especially the production and distribution of supplies, post-war economic policies, and national security. The series also includes Eberstadt's correspondence with politicians, academics, and concerned citizens discussing these issues, as well as correspondence with his colleagues in the investment field regarding his business and investing, and correspondence with policy, social, and charity organizations regarding his membership and their meetings and causes.

Eberstadt's personal correspondence with his family is located in Series 14: Personal and Family Records.