Iowa - Criteria: A (event)
| Janko, Jan F. and Antonie, Farmstead District |
| Jefferson Elementary School |
| Jefferson Square Commercial Historic District |
| Jefferson Street Historic District |
| Johnson County Courthouse |
| Johnson, George, House |
| Johnson, William A. and Ida C., House |
| Johnstone, Dr. Anna E. and Andrew A., House |
| Jones County Court House |
| Jones Creek Watershed Historic District |
| Jones, G.W., Building |
| Kellogg, Miles and Elizabeth Smith, House |
| Kent Union Chapel and Cemetery |
| Keokuk National Cemetery |
| Keokuk Union Depot |
| Keokuk Young Women's Christian Association Building |
| Kerndt G., and Brothers Elevator and Warehouses, No. 11, No.12 and No. 13 |
| Kerndt, G., & Brothers Office Block |
| Kimballton Commercial District |
| Kimballton West 2nd-West 3rd Street Residential District |
| Kingman Place Historic District |
| King Memorial Chapel |
| Kinney Octagon Barn |
| Kirchner, Philip and Anna Parrish, Log House |
| Kirkham, Francis M., House |
| Klondike Hotel |
| Klose, Dr. William H. and Mae R., House |
| Knapp-Wilson House |
| Knotts, Nellie and Thomas, House |
| Knoxville Veterans Administration Hospital Historic District |
| Knoxville WPA Athletic Field Historic District |
| Koch, Hans M., House |
| Koren Library |
| Kreinbring Phillips 66 Gas Station |
| Kromer Flats |
| Kurtz, Glenn and Nell, Lustron Home and Garage |
| Kvindherred Lutheran Church, School and Cemetery |
| Lagomarcino-Grupe Company |
| Lake City Community Memorial Building |
| Lake City Public Library |
| Lake City Water Standpipe |
| Lakeside Ballroom |
| Lakeside Park Historic District |
| Lamm-Pollmiller Farmstead District |
| Lange, August H. J. and Justena, Farmstead Historic District |
| Langworthy Historic District |
| Lansing Fisheries Building |
| Lansing Main Street Historic District |
| Lansing Stone School |
| La Porte City Station |
| LaPorte City Town Hall and Fire Station |
| Lattner Auditorium Building |
| Laurens Carnegie Free Library |
| Lee County Courthouse |
| Leeds Junior High School |
| Leet, William A., and Frederick Hassler Farmstead District |
| Le Mars Downtown Commercial Historic District |
| Le Mars Municipal Park and Golf Course Historic District |
| Lenox Hotel |
| Lenox Township Church of the New Jersalem |
| Lesinger Block |
| Lewis Hotel |
| Lewis System Armored Car and Detective Service Building |
| Liberty Building |
| Liberty Hall |
| Lime Springs Mill Complex |
| Lincoln-Fairview Historic District |
| Lincoln Highway Bridge |
| Lincoln Hotel |
| Lincoln School |
| Lincoln Statue |
| Linden Heights Historic District |
| Linograph Company Building, The |
| Lisbon Main Street Historic District |
| Lisbon Methodist Church |
| Littig Brothers/Mengel & Klindt/Eagle Brewery |
| Lock and Dam No. 11 Historic District |
| Lock and Dam No. 12 Historic District |
| Lock and Dam No. 14 Historic District |
| Lock and Dam No. 16 Historic District |
| Lock and Dam No. 19 Historic District |
| Locust School |
| Logan Center School No.5 |
| LONESTAR |
| Longfellow Historic District |
| Lord, Richard T. C., and William V. Wilcox House |
| Louden Monorail System in the Auto Repair Shop |
| Louden, R. Bruce and May W., House |
| Louden, R.R., and Antoinette, House |
| Louden Whirl-Around |
| Lucas County Courthouse Square Historic District |
| Luedtke, August and Vera, Barn |
| Luther College Farm |
| Lu Verne City Jail |
| Lynnville Mill and Dam |
| Lyon Block |
| Mack-International Motor Truck Corporation Building |
| Maine, The |
| Manning Commercial Historic District |
| Mann School No. 2 |
Data from United States Park Service and Wikidata
