- Admiral John Randolph Tucker Papers, 1865/18972
- Adolphus DeBussey, Soldier, Civil War Letters, 1861/1998, bulk 1861/187114
- Adolphus P. Howard Papers, 1850/19381
- Adolphus P. Howard Papers, 1854/19041
- Advisory Committee Research Collection, 1772/201713
- Affidavit of Francis Crawford and Margaret Crawford, 1861/18651
- African American Stereoview Collection, 1860/19011
- African and African American photograph collection, 1850/19451
- Aileen Shafer, Collector, Material regarding African-Americans, 1829/18845
- Alabama Collection, 1823/18932
- Alan Clarke Railroad Research Papers, 1861/20122
- Albert Frederick Wilson papers, 1840/19343
- Albert R. Gallatin papers, 1795/18281
- Albert Taylor Bledsoe and Sophia Bledsoe Herrick letters, 1858/19082
- Alderman family papers, 1779/19616