I
- Iliff, Colorado – John Wesley Iliff (cattleman)
- Imusdale, California – Chales, Edwin, and William Imus (early settlers)
- Ira, Vermont – Ira Allen (one of the Green Mountain Boys and brother of Ethan Allen)
- Irasburg, Vermont – Ira Allen (landholder, one of the Green Mountain Boys and brother of Ethan Allen)
- Irvine, California – James Irvine I
- Irwin, California – W.A. Irwin (founder)
- Isabella, California – Queen Isabella of Spain
- Isle La Motte, Vermont – Captain La Motte (established Fort Sainte Anne on this island)
- Iverson, California – Charles Iverson
Read more about this topic: List Of American Places Named After People