Collection
- Addison D. and Minerva Skinner collection, 18641
- Adeline Hart collection, 1837-1859 (majority within 1850-1859)1
- Adlai Stevenson collection, 1860-19621
- African American and African Diaspora collection, 1729-1970 (majority within 1781-1865)1
- Agnes Leeds letters, 1842-18431
- Alaska collection, 1889-18951
- Albert E. St. Germain collection, 1894-1964 (majority within 1917-1919)1
- Albert Morrison collection, 1841-18861
- Albert Starke Drischell collection, 1943-19451
- Albert W. Stahl collection, 1883-18901
- Alexander Lyman Holley letters, 1841-18671
- Alexander T. Stewart collection, 1855-1876 (majority within 1863-1876)1
- Alexander Thompson papers, 1793-19321
- Alexander Wedderburn, 1st Earl of Rosslyn papers, 1676-1801 (majority within 1764-1800)1
- Alexander Wilson collection, 1845-18461
- Alexandre Maurice Blanc de Lanautte, Comte d'Hauterive collection, 18091
- Alexis St. Martin collection, 18791
- Alfred C. and Cordelia Arnold papers, 1862-18651
- Alfred P. Sawyer letters, 1875-1878 (majority within 1877-1878)1
- Alfred Schaller letters, 1917-19191