Iowa - Area of significance: Architecture
| Holy Ghost Catholic Historic District |
| Holy Guardian Angels Church and Cemetery Historic District |
| Holy Trinity Greek Orthodox Church |
| Homestead Building |
| Honey Creek Friends' Meetinghouse |
| Hoosier Row School |
| Hope Fire Company Engine House |
| Hornback, Emily, House |
| Horn House |
| Hose Station No. 1 |
| Hose Station No. 6 |
| Hose Station No. 7 |
| Hotel Burlington |
| Hotel Charitone |
| Hotel Chieftain |
| Hotel Fort Des Moines |
| Hotel Hurst |
| Hotel Hurst Garage |
| Hotel Iowa |
| Hotel Kirkwood |
| Hotel Manning |
| Hotel Mealey |
| Hotel Mississippi-RKO Orpheum Theater |
| Hotel Ottumwa |
| Hotel President |
| Hotel Randolph |
| Hotel Rea |
| Hotel Roosevelt |
| 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 |
| 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 |
| Humboldt Free Public Library |
| Hunter School |
| Hurst, A. A., House |
| Ida County Courthouse |
| Ijem Avenue Commercial Historic District |
| Illinois Central Combination Depot-Ackley |
| Illinois Central Passenger Depot-Storm Lake |
| Illinois Central Railroad Yard-Cherokee |
| Immanuel Danish Evangelical Lutheran Church |
| Indianola Carnegie Library |
| Indianola High School |
| Ingersoll Place Plat Historic District |
| Insane Asylum at the County Poor Farm |
| Interior Telephone Company Building |
| International Harvester Truck Sales and Service Station |
| IOOF Building |
| I.O.O.F. Hall |
| I.O.O.F. Hall |
| 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 Falls Union Depot |
| Iowa Ford Tractor Company Repair and Warehouse Building |
| Iowa Lakeside Laboratory Historic District |
| Iowa Men's Reformatory Historic District |
| Iowan's Hotel |
| Iowa Soldiers' Orphans' Home |
| Iowa State Capitol |
| Iowa State Fair and Exposition Grounds Historic District |
| Iowa State Historical Building |
| Iowa State Penitentiary Cellhouses Historic District |
| Iowa Wind Mill and Pump Company Office and Warehouse |
| Iowa Yearly Meeting House-College Avenue Friends Church |
| Jackson County Courthouse |
| 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 Street Historic District |
| Jenkins, Dr. George A., House |
| Jewell Apartments |
| 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 |
Data from United States Park Service and Wikidata
