- A.B. Stickney, Compiler, Genealogical Materials, 1838/19591
- A.E.S. Stephens Papers, 1949/19611
- A.J. Morrison Collection, 1754/19751
- A.S. Hammack papers, 1864/19541
- Aaron Chipps, Coal Miner, Papers, 1912/19551
- Abbye A. Gorin Architectural Collection, 1940/2006, bulk 1995/20061
- Abraham Anson papers, 1939/20051
- Abraham Lincoln Collection, 1860/19651
- Ada Haldeman Ford, Suffragist, Papers, 1900/19701
- Adalbert J. Volck Collection of Etchings, 1861/19791
- Adam Empie Papers, 1811/2004, bulk 1811/18501
- Adams T. Rice papers, 1922/19601
- Addison H. Smith papers, 1917/1970, bulk 1917/19221
- Adele Blow Chatfield-Taylor family papers, 1899/19771
- Adele Goodman Clark papers, 1849/19781