Iowa - Criteria: A (event)
| Gull Point State Park, Area A |
| Gull Point State Park, Area B |
| Guttenberg Corn Canning Co. |
| Guttenberg National Fish Hatchery and Aquarium Historic District |
| Hamburg Historic District |
| Hamburg Public Library |
| Hampton Double Square Historic District |
| Haner, William, Polygonal Barn |
| Hansen, Andrew P., Farmstead |
| Harbach, L. and Sons Furniture Warehouse and Factory Complex |
| Hardacre Theater |
| Hardin County Home Historic District |
| Harmon and LeValley Northwest Historic District |
| Harper and McIntire Company Warehouse |
| Harris, Dr. Percy and Lileah, House |
| Hauschild's Hall |
| Hawarden City Hall, Fire Station and Auditorium |
| Hawkeye Insurance Company Building |
| Hawkeye Transfer Company Warehouse |
| Hawthorne Glove and Novelty Company-Shrader Drug Company Building |
| Hayes, William B., House |
| Hebard, Alfred, House |
| Hedge Block |
| Helvig-Olson Farm Historic District |
| Henderson, Daniel and Nancy Swaford, House |
| Henn Mansion |
| Heritage Hill Historic District |
| Herring Hotel |
| Herring Motor Car Company Building |
| Hibernia Hall |
| Highland Historic District |
| Highland Park Historic Business District at Euclid and Sixth Avenues |
| Highlandville School |
| Hippee Building |
| Historic Railroad District |
| Hitchcock, Rev. George B., House |
| Hofmann Building |
| Holmes, John S. and Elizabeth Beem, Barn |
| Holtkamp Round Barn |
| Holy Ghost Catholic Historic District |
| Holy Trinity Greek Orthodox Church |
| Home of Marshall's Horseradish |
| Homestead Building |
| Hoosier Row School |
| Hope Fire Company Engine House |
| Hornback, Emily, House |
| Hose Station No. 1 |
| Hose Station No. 6 |
| Hotel Burlington |
| Hotel Charitone |
| Hotel Chieftain |
| Hotel Greenfield |
| Hotel Hurst |
| Hotel Hurst Garage |
| Hotel Kirkwood |
| Hotel Lester-Lester Cafe |
| Hotel Mealey |
| Hotel Mississippi-RKO Orpheum Theater |
| Hotel Ottumwa |
| Hotel President |
| Hotel Russell-Lamson |
| Hotel Tipton |
| Hotel Whitney |
| Howes Building |
| Hubbell Building |
| Hubbell Warehouse |
| Hughes-Irons Motor Company |
| Hult, Charles E., House, Summer Kitchen and Wood Shed |
| Humboldt County Court House |
| Hurstville Historic District |
| Ida County Courthouse |
| Illinois Central Railroad Yard-Cherokee |
| Immanuel Danish Evangelical Lutheran Church |
| Indianola Carnegie Library |
| Indianola High School |
| Ingemann Danish Evangelical Lutheran Church and Cemetery |
| Ingersoll Place Plat Historic District |
| Interstate Power Company Building |
| IOOF Building |
| I.O.O.F. Hall |
| I.O.O.F. (International Order of Odd Fellows) Valley Junction Lodge Hall No. 604 |
| Iowa Building |
| Iowa Canning Company Seed House Building |
| Iowa Falls Union Depot |
| Iowa Lakeside Laboratory Historic District |
| Iowa Malleable Iron Company |
| Iowa Men's Reformatory Historic District |
| Iowana Hotel |
| Iowan's Hotel |
| Iowa Reform Building |
| Iowa Soldiers' Orphans' Home |
| Iowa State Capitol |
| Iowa State Fair and Exposition Grounds Historic District |
| Iowa State Highway Commission, District 6 Building |
| Iowa Wind Mill and Pump Company Office and Warehouse |
| Iowa Yearly Meeting House-College Avenue Friends Church |
| Iron Post |
| Irwin Consolidated School |
| Jackson County Courthouse |
| Jackson County Jail |
Data from United States Park Service and Wikidata
