Iowa - Significance region: Local
| Hotel Randolph |
| Hotel Rea |
| Hotel Roosevelt |
| Hotel Russell-Lamson |
| Hotel Tipton |
| Hotel Whitney |
| House at 111 E. Maple Street |
| House at 1646 W. Second Street |
| House at 2123 W. Second Street |
| House at 2212 W. River Drive |
| House at 318-332 Marquette Street |
| House at 505 Court Street |
| House at 919 Oneida Street |
| Howard County Courthouse |
| Howes Building |
| Hubbard Park |
| Hubbell Building |
| Hubbell Warehouse |
| Hughes, David and M. Maria, House |
| Hughes-Irons Motor Company |
| Hughes, Martin, House |
| Hulme, Samuel and Sarah, House |
| Hult, Charles E., House, Summer Kitchen and Wood Shed |
| Humboldt County Court House |
| Hunter School |
| Hurst, A. A., House |
| Ida County Courthouse |
| Ijem Avenue Commercial Historic District |
| Imes Covered Bridge |
| Immanuel Danish Evangelical Lutheran Church |
| Indianola Carnegie Library |
| Indianola High School |
| Ingemann Danish Evangelical Lutheran Church and Cemetery |
| Ingersoll Place Plat Historic District |
| Insane Asylum at the County Poor Farm |
| Interior Telephone Company Building |
| International Harvester Truck Sales and Service Station |
| Interstate Power Company Building |
| IOOF Building |
| I.O.O.F. Hall |
| I.O.O.F. Hall |
| I.O.O.F. (International Order of Odd Fellows) Valley Junction Lodge Hall No. 604 |
| Iowa Beta Chapter of Sigma Phi Epsilon |
| Iowa Building |
| Iowa Canning Company Seed House Building |
| Iowa City Community Recreation Center |
| Iowa City Downtown Historic District |
| Iowa County Courthouse |
| Iowa-Des Moines National Bank Building |
| Iowa Ford Tractor Company Repair and Warehouse Building |
| Iowa Malleable Iron Company |
| Iowa Mutual Insurance Company Home Office |
| Iowana Hotel |
| Iowan's Hotel |
| Iowa Reform Building |
| Iowa State Highway Commission, District 6 Building |
| Iowa State Historical Building |
| Iowa Wind Mill and Pump Company Office and Warehouse |
| Iowa Yearly Meeting House-College Avenue Friends Church |
| Irwin Consolidated School |
| Irwin, John N. and Mary L. (Rankin), House |
| Jackson County Courthouse |
| Jackson County Jail |
| Jackson Park Historic District |
| Jackson-Swisher House and Carriage House |
| Jacobson Farm |
| Jagger-Churchill House |
| Janko, Jan F. and Antonie, Farmstead District |
| Jansen, Theodore, House |
| Jasper County Courthouse |
| Jay Funeral Home |
| Jefferis, Thomas, House |
| Jefferson County Courthouse |
| Jefferson Elementary School |
| Jefferson Square Commercial Historic District |
| Jefferson Street Historic District |
| Jenkins, Dr. George A., House |
| Johnson, Capt. Nicholas W. and Emma, House |
| Johnson County Courthouse |
| Johnson County Poor Farm and Asylum Historic District |
| Johnson County Savings Bank |
| Johnson, George, House |
| Johnson, Mrs. Lydia, House |
| Johnson, Sylvanus, House |
| Johnson, William A. and Ida C., House |
| Johnstone, Dr. Anna E. and Andrew A., House |
| Jones Business College |
| Jones County Court House |
| Jones, G.W., Building |
| Jorgensen, Hans J., Barn |
| Joy, C. R., House |
| Kahl, Henry, House |
| Kattenbracher House |
| Keck, Joseph, House |
| Keeler, Rev. R. W. and Fannie E., House |
| Keerl-Decker House |
| Kegler Gonner Store and Post Office |
| Kelley House |
| Kellogg, Miles and Elizabeth Smith, House |
| Kellow House |
Data from United States Park Service and Wikidata
