- Hurricane Hugo Oral History Collection, 200911
- Hutson Lee Papers, 1858-186515
- Illustrated Newspaper Clippings, 1840-191739
- In Camp And At The Front, WW1 Selections, South Carolina Political Collections173
- Independent Republic Quarterly164
- Indexes of Local History and Genealogy22
- Inventory of S.C. Church Archives283
- Invoice of rice sales for Anthony Clarkson, 1762 Oct. 301
- Irish Heritage Oral History Collection32
- Is part of: William Lynch Postcard Collection1
- Isaac Harby Family Papers6
- Isaac Hayne Journal: Register, ca. 1764-17811
- Isaac Rosenberg: Early Poetry and Related Documents from the Joseph Cohen Collection of World War I Literature10
- Isaac Samuel Leevy Papers, 1905-197333
- Isabella Sarah Porcher Plantation Prescription Book1
- Isaiah Bennett Papers, ca. 1932-200226
- Isaiah DeQuincey Newman Papers1,465
- J. Arthur Brown Papers, 1937 - 1988380
- J. Marion Sims Letters4
- James Calvin Hemphill, Sr. Architectural Collection94