- 1st New York Mounted Rifles letter, 18641
- A. H. Hand Papers, 1835/20091
- Abolitionist Movement Collection, 1834/18881
- Adams Papers, 1782/18901
- Adee Family Papers, 1862/18651
- Alabama Collection, 1823/18931
- Alamby Miller Scrapbook, 1864/18701
- Albert C. Swindler Papers, 1862/1929, bulk 1862/18641
- Albert N. Hubbard Letter, 18641
- Alexander Brown Papers (I), 1815/19101
- Alexander Brown Papers (II), 1748/19001
- Alexander Haight family collection, 1764/19761
- Alexander Hamilton, Jr. Letters, 1832/18331
- Alexander Lockhart Nelson papers, 1848/19021
- Alexander M. Davis Papers, 1850/18921