- Hôtel Karersee3
- International Joint Commission3
- Iowa Geological Survey3
- Iowa. Board of Railroad Commissioners3
- Iowa. Board of Railroad Commissioners.3
- Iowa. Highway Commission3
- Iowa. State Planning Board. Recreation & Historic Division3
- Irvine, William, 1741-18043
- J. Pigot & Co.3
- Jentzsch, Alfred, 1850-19253
- Johnston, Alexander Keith, 1804-18713
- Julius Bien & Co.3
- Keere, Pieter van den, 1571-approximately 16463
- Kenyon Company3
- Keulen, Gerard van3
- Klooz, C. J.3
- L'Enfant, Pierre Charles, 1754-18253
- Lagrive, Jean de, 1689-17573
- Lamb, George3
- Lapham, Increase Allen, 1811-18753