Iowa - Area of significance: Architecture
| Johnson, Mrs. Lydia, House |
| Johnson, Sylvanus, 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 Building |
| Kahl, Henry, 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 |
| Kendall Young Public Library |
| Kenny Farmstead Archeological District |
| Keokuk County Courthouse |
| Keokuk Lock and Dam |
| Keokuk National Cemetery |
| Keokuk Union Depot |
| Keokuk Young Women's Christian Association Building |
| Kidder, Zephaniah, House |
| Kiene, Albert, House |
| Kimball-Stevenson House |
| Kimballton Commercial District |
| Kimballton West 2nd-West 3rd Street Residential District |
| Kingman Place Historic District |
| King Memorial Chapel |
| King Tower Historic District |
| Kinney Octagon Barn |
| Kirkpatrick, Robert Round Barn |
| Kirk, The |
| Kirkwood House |
| Klindt, George, House |
| Klindt, Henry, House |
| Klinsky Farmstead Historic District |
| Knott, Adams R., Frederick L. and Martha (Taylor), House |
| Knott, Dr. Van Buren, House |
| Knoxville Veterans Administration Hospital Historic District |
| Knoxville WPA Athletic Field Historic District |
| Koch Drug Store |
| Koch, Hans M., House |
| Koelman, Philipus J. and Cornelia, House |
| Koenig Building |
| Koester, Nicholas, Building |
| Kolker House |
| Koren Library |
| Kreinbring Phillips 66 Gas Station |
| Kromer Flats |
| Kucheman Building |
| Kuhnen, Nicholas J., House |
| Kurtz, Glenn and Nell, Lustron Home and Garage |
| Kurtz House |
| Kyte, John and Mary Jane, Farmstead District |
| Lacey-Keosauqua State Park, Bathing Area (Area C) |
| Lacey-Keosauqua State Park, Lodge and Picnic Area (Area A) |
| Lacey-Keosauqua State Park, Picnic and Custodial Group (Area B) |
| Ladora Savings Bank |
| Lake Ahquabi State Park, Bathhouse Area (Area B) |
| Lake Ahquabi State Park, Picnic Area (Area A) |
| Lake Ahquabi State Park, Refectory Area (Area C) |
| Lake City Community Memorial Building |
| Lake City Public Library |
| Lake, John, House |
| Lake Keomah State Park, Bathhouse-Lodge Area (Area A) |
| Lakeside Park Historic District |
| Lamberson, Jack, House |
| Lamb, Lafayette, House |
| Lancaster School |
| Land and Loan Office Building |
| Lane, Samuel M., House |
| Lange, August H. J. and Justena, Farmstead Historic District |
| Langworthy Historic District |
| Langworthy House |
| Lansing Main Street Historic District |
| Lansing Stone School |
| Larsen, Chris, House |
| Larsen, Jens T., House |
| Lattner Auditorium Building |
| Laurens Carnegie Free Library |
| LeClaire, Antoine, House |
| Lee, Captain Daniel S. and Fannie L. (Brooks), House |
| Leeds Junior High School |
| Leet, William A., and Frederick Hassler Farmstead District |
| Leith, Doctor Alexander R. (A.R.) and Louisa J., House |
| Le Mars Central High School |
| Le Mars Public Library |
| Lenox Round Barn |
| Lerch, Gustov C., House |
| Lesinger Block |
| Lewis Hotel |
| Lexington, The |
| Liberty Building |
| Liberty Hall |
| Lincoln Elementary School |
| Lincoln-Fairview Historic District |
| Lincoln School |
Data from United States Park Service and Wikidata
