Iowa - Criteria: B (person)
| Johnson, George, House |
| Jones Business College |
| Jordan House |
| Jorgensen, Hans J., Barn |
| Kahl, Henry, House |
| Kattenbracher House |
| Kerndt, G., & Brothers Office Block |
| Kirkham, Francis M., House |
| Kirk, The |
| Kirkwood House |
| Klindt, George, House |
| Knapp-Wilson House |
| Kuhnen, Nicholas J., House |
| Lamb, Lafayette, House |
| Lane, Lucius and Maria Clinton, House |
| Langworthy Historic District |
| Langworthy House |
| LeClaire, Antoine, House |
| Letovsky-Rohret House |
| Lewelling, Henderson, House |
| Lewis Hotel |
| Lewis System Armored Car and Detective Service Building |
| Lincoln-Fairview Historic District |
| Lincoln School |
| Louden, R. B. and Lizzie L., House |
| Louden, William and Mary Jane, House |
| Luther College Farm |
| MacDonald, Gilmour B. and Edith Craig, House |
| Manatt, William, House |
| Mason City YMCA |
| Masonic Temple |
| McCaffrey House |
| McColl, Anthony M., House |
| McCollister, James, Farmstead |
| McGee School |
| McKibben, S. M., House |
| McWaid, Job A. and Rebecca E., House |
| Melrose Historic District |
| Mentzer, Joseph P., House |
| Miller, F. H., House |
| Miller, Justice Samuel Freeman, House |
| Miller, Severin, House |
| Montauk |
| Moorehead Stagecoach Inn |
| Morningside College Historic District |
| Motor Townsite |
| Murphy, Thos. D. Co. Factory And Power Plant |
| Mylius-Eaton House |
| "Nebergall ""Knoll Crest"" Round Barn" |
| Netcott-Pfeiffer House |
| Newens Sanitary Dairy Historic District |
| New Orpheum Theatre |
| Nichols, Samuel, House |
| Noble-Kendall House |
| Oakes-Wood House |
| Old Fourth Ward Southeast Historic District |
| Old Mill House |
| Oleson Park Music Pavilion |
| Ormsby-Kelly House |
| Osborne, Edmund B., House |
| Palmer, B. J., House |
| Paradise Farm |
| Park/Glen Avenues Historic District |
| Parr, Charles Henry, House |
| Peak, George B., House |
| Peoples Nationals Bank |
| Peterson Manufacturing Building |
| Pine Creek Gristmill |
| Pioneer Implement Company |
| Plum Grove |
| Potter's, E. G., Jasper Flour Mill |
| Rambo House |
| Ray, Frank G., House & Carriage House |
| Reeves, Isaac and Agnes (Bells), House |
| Renken, Renke and Wubke, House |
| "Reynolds, Joseph ""Diamond Jo,"" Office Building and House" |
| Rogers-Knutson House |
| Russell, Rensselaer, House |
| Saint Boniface Catholic Church District |
| Saint Irenaeus Church |
| Salisbury House |
| Sample, Hugh W. and Sarah, House |
| Sanford, Arthur and Stella, House |
| Schlapp, George E., House |
| Scholte, Dominie Henry P., House |
| Sergeant Floyd Monument |
| Shaw, Col. William T. and Elizabeth C., House |
| Sheaffer, Walter A., House |
| Sherman Nursery Company Historic District |
| Shimek, Bohumil, House |
| Singmaster, C.F. and Mary, House |
| Smith, John, House |
| Smith, Peter and Mary, House |
| Smouse, Winfield, House |
| Spencer High School and Auditorium |
| Spencer, Roswell, House |
| Squiers, J. E., House |
| Starker-Leopold Historic District |
| State Quarry, Old |
| Stewart Library |
Data from United States Park Service and Wikidata
