Series I: Papers and Volumes, 1829-1876 (bulk 1845-1876) contains copies of letters and documents published in The Papers of Andrew Johnson. The Project gathered primary documents from such institutions as the Tennessee State Library and Archives, the Historical Society of Pennsylvania, the Huntington Library, the New York Public Library, the Massachusetts Historical Society, Duke University Library, the Library of Congress, and the National Archives and Records Administration (NARA). Copies of the handwritten original letters are occasionally accompanied by typed and proofread transcriptions. This series also houses drafts, materials used to write introductions and explanatory notes, and microfilm from NARA containing copies of primary documents from the Office of the Treasury, the Department of State, the United States Army, and other branches of the government dating from 1837 to 1878.

Series II: Research Files, 1837-1984 (bulk 1864-1984) houses unpublished materials, including correspondence, Supreme Court and Congressional records, military service records, pension records, and handwritten notes.

Series III: Administrative Papers, 1854-2000 (bulk 1957-2000) contains the Project's internal records, including payroll and personnel files, biographical information on Johnson and other figures, newspaper and journal articles, book reviews, excerpts from books about the period, budgets, grant proposals, press and public relations documents, and photographs (including images of President Lyndon Johnson accepting a copy of the first published volume of the set).