- Ice Skate Company Account Book, 1859/18652
- Inge Horton Architectural Collection, 1964/19995
- Institute for the History of Technology and Industrial Archaeology Records, 1875/2005, bulk 1980/200512
- International Association for Identification Records, 1842/2012, bulk 1910/19595
- Ira E. Robinson Papers, 1818/19301
- Ira F. Gensel Letter, 18621
- Irvine-Saunders Family Papers
1745-1910 Inclusive14
- Isaac & Josiah Williams Brick Company, Account Books, 1844/19901
- Isaac B. Smith, Farmer and Music Teacher, Newspaper Clippings and Other Material, 1840/19841
- Isaac Campbell Account Book, 1834/18632
- Isaac Caruthers, Monroe County Merchant, Store and Tavern Ledgers, 1819/18631
- Isaac Cox Letter, 18622
- Isaac Horne Ledgers, 1824/18702
- Isaac L. Carey Correspondence, 1850s-1867, 1850/18672
- Isaac M. Clark Letter, 18621