- A. H. Hand Papers, 1835/20091
- Abner Johnson Leavenworth Papers, 1825/18611
- Abolitionist Movement Collection, 1834/18881
- Adams Papers, 1782/18901
- Alabama Collection, 1823/18931
- 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
- Alfred Leyburn Papers, 1823/1899, bulk 1830/18391
- Allen-Kean-Laurence family letters, 1837/19601
- Alumni Association Records, 1833/2014, bulk 1950/20051
- Amos Koontz Papers I, 1809/1965, bulk 1936/19651