- A.M. Scott Correspondence, 1874/18821
- A.S. Hammack papers, 1864/19541
- Abbie Louisa Hill Scrapbook, 1874/18841
- Abner Osburn, Physician, Papers, 1846/19011
- Abolitionist Movement Collection, 1834/18881
- Abraham Lincoln Collection, 1860/19651
- Account Books, 1782/18951
- Account book (N.H.), 1856/18741
- Accounts, 19th Century, 1836/18971
- Adalbert J. Volck Collection of Etchings, 1861/19791
- Adam Empie Papers, 1811/2004, bulk 1811/18501
- Adams Papers, 1782/18901
- Adele Goodman Clark papers, 1849/19781
- Adin B. Underwood Papers, 1861/19261
- Administration records collection, 1776/19761