Iowa - Role: District
| Lamm-Pollmiller Farmstead District |
| Lange, August H. J. and Justena, Farmstead Historic District |
| Langworthy Historic District |
| Lansing Main Street Historic District |
| Leet, William A., and Frederick Hassler Farmstead District |
| Le Mars Downtown Commercial Historic District |
| Le Mars Municipal Park and Golf Course Historic District |
| Lewis, Judge W.H. and Emma, Historic District |
| Lincoln-Fairview Historic District |
| Lincoln Highway-Buttrick's Creek to Grand Junction Segment |
| Lincoln Highway-Grand Junction Segment |
| Lincoln Highway-Raccoon River Rural Segment |
| Lincoln Highway-West Beaver Creek Abandoned Segment |
| Lincoln Highway-West Greene County Rural Segment |
| Linden Heights Historic District |
| Lisbon Main Street Historic District |
| 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 |
| Longfellow Historic District |
| Loras College Historic District |
| Lucas County Courthouse Square Historic District |
| Luther College Campus Historic District |
| Manning Commercial Historic District |
| Manufacturing and Wholesale Historic District |
| Maquoketa Caves State Park Historic District |
| Maquoketa Commercial Historic District |
| Marion Commercial Historic District |
| Marshalltown Downtown Historic District |
| Marycrest College Historic District |
| Mason City Downtown Historic District |
| May's Island Historic District |
| McClellan Heights Historic Dictrict |
| McColm, Laura Musser, Historic District |
| McGregor Commercial Historic District |
| Melrose Historic District |
| Meyers Farmstead Historic District |
| Middlesex Plat Historic District |
| Mills Tower Historic District |
| Milwaukee Railroad Shops Historic District |
| Mines of Spain Area Rural Community Archeological District |
| Mines of Spain Lead Mining Community Archeological District |
| Mines of Spain Prehistoric District |
| Mini-Wakan State Park Historic District |
| Minor, Josias L. and Elizabeth A., Farmstead District |
| Monroe Elementary School Historic District |
| Montezuma Downtown Historic District |
| Morningside College Historic District |
| Motor Mill Historic District |
| Motor Townsite |
| Mount Vernon Commercial Historic District |
| Muscatine Avenue Moffitt Cottage Historic District |
| Nevada Downtown Historic District |
| Newens Sanitary Dairy Historic District |
| Newton Downtown Historic District |
| North Fellows Historic District |
| North Grand Avenue Residential Historic District |
| North Grinnell Historic District |
| Northwood Central Avenue Historic District |
| Notbohm Mill Archaeological District |
| Oak Hill Cemetery Historic District |
| Oak Hill Historic District |
| Oakland Cemetery |
| Oaklands, The, Historic District |
| Oak Lane Historic District |
| Old Fourth Ward Southeast Historic District |
| Old Lenox College |
| Old Main Historic District |
| Old Settlers' Association Park and Rhodham Bonnifield House |
| Old Town Historic District |
| Osage Commercial Historic District |
| Osceola Commercial Historic District |
| Oskaloosa City Park and Band Stand |
| Oskaloosa City Square Commercial Historic District |
| Ottumwa Cemetery Historic District |
| Our Mother of Sorrows Grotto Historic District |
| Owl's Head Historic District |
| Oxford Commercial Historic District |
| Parker's Woods Park Historic District |
| Park/Glen Avenues Historic District |
| Park-to-Park Residential Historic District |
| Penn College Historic District |
| Pentacrest |
| Pikes Point State Park Shelter and Steps |
| Pilot Knob State Park: Portals in Area 5b |
| Pilot Knob State Park, Trail Area (Area 6a-6c) |
| Pleasant Lawn School Historic District |
| Pleasant View Stock Farm Historic District |
| Podhajsky-Jansa Farmstead District |
| Polk County Homestead and Trust Company Addition Historic District |
| Poplar Rural District |
| Preston’s Station Historic District |
| Prospect Park Historic District |
| Prospect Park Second Plat Historic District |
| Public Square Historic District |
| Pucker Street Historic District |
| Putnam-Parker Block |
| Redmond Park-Grande Avenue Historic District |
Data from United States Park Service and Wikidata
