- IAWA Small Collections, 1907/20132
- IAWA: International Archive of Women in Architecture Records, 1967/2013, bulk 1985/20081
- Independent Order of St. Luke Records, 1877/19703
- Inge Horton Architectural Collection, 1964/199977
- Institute for the History of Technology and Industrial Archaeology Records, 1875/2005, bulk 1980/200521
- Instructive Visiting Nurses Association records, 1902/19998
- Internal Library Records, 1923/20231
- International Association for Identification Records, 1842/2012, bulk 1910/195934
- International Order of Odd Fellows, Lodge 134, Ledgers, 1892/19281
- Ira E. Robinson Papers, 1818/19301
- Ira E. Robinson Papers, 1869/19511
- Ira E. Robinson Papers, 1898/19101
- Iron Gate, Virginia, Ledgers, 1892/19311
- Irvine-Saunders Family Papers
1745-1910 Inclusive11
- Isaac & Josiah Williams Brick Company, Account Books, 1844/19901