- Ice Skate Company Account Book, 1859/18652
- Inge Horton Architectural Collection, 1964/19997
- Institute for the History of Technology and Industrial Archaeology Records, 1875/2005, bulk 1980/200512
- International Association for Identification Records, 1842/2012, bulk 1910/19596
- Ira E. Robinson Papers, 1818/19301
- Irvine-Saunders Family Papers
1745-1910 Inclusive13
- Isaac & Josiah Williams Brick Company, Account Books, 1844/19901
- Isaac B. Smith, Farmer and Music Teacher, Newspaper Clippings and Other Material, 1840/19841
- Isaac Brill and Lemuel Arnold, Civil War Soldiers' Letters, 18631
- Isaac Campbell Account Book, 1834/18632
- Isaac Caruthers, Monroe County Merchant, Store and Tavern Ledgers, 1819/18631
- Isaac Horne Ledgers, 1824/18702
- Isaac L. Carey Correspondence, 1850s-1867, 1850/18672
- Isaac McNeel (b.1830) Papers, 1850/19081
- Isaac N. Baker Civil War memoirs, 1863/18641