Delaware - Criteria: C (architecture/engineering)
| McCoy House |
| McDaniel, Delaplane, House |
| McDaniel, J., Farm |
| McIntyre, J., Farm |
| McWhorter House |
| Meeteer House |
| Melson House |
| Memorial Hall |
| Merestone |
| Messick, Dr. John W., House and Office |
| Meteer Store House |
| Middletown Academy |
| Middletown Historic District |
| Mifflin-Marim Agricultural Complex |
| Milford New Century Club |
| Milford Shipyard Area Historic District |
| Mill Creek Friends Meetinghouse |
| Mill House |
| Milton Historic District |
| Mispillion Lighthouse and Beacon Tower |
| Misty Vale |
| Mondamon Farm |
| Montchanin Historic District |
| Monterey |
| Montgomery House |
| Moore House |
| Moore Potato House |
| Mordington |
| Morgan, William, Farm |
| Morrow, James, House |
| Mount Cuba |
| Mount Cuba Historic District |
| Mount Lebanon Methodist Episcopal Church |
| Mount Pleasant |
| Mount Pleasant Methodist Episcopal Church and Parsonage |
| Mt. Airy School No. 27 |
| Naaman's Creek School |
| Naudain, Arnold S., House |
| Nelson, John B., House |
| Newark Opera House |
| Newark Passenger Station |
| New Castle and Frenchtown Railroad Right-of-Way |
| New Castle County Court House |
| New Castle Historic District |
| New Castle Ice Piers |
| New Castle Leather Raw Stock Warehouse |
| New Century Club |
| Newport National Bank |
| Newport Railroad Station |
| North Milford Historic District |
| North Saint Georges Historic District |
| Norwood House |
| Noxontown |
| Octagonal Schoolhouse |
| Odessa Historic District |
| Okolona |
| Old Asbury Methodist Church |
| Old Bridgeville Fire House |
| Old Cann Mansion House |
| Old Christ Church |
| Old College Historic District |
| Old Customshouse |
| Old Drawyers Church |
| Old First Presbyterian Church |
| Old First Presbyterian Church of Wilmington |
| Old Fort Church |
| Old Post Ofice |
| Old St. Anne's Church |
| Old Statehouse |
| Old Stone Tavern |
| Old St. Paul's Methodist Episcopal Church |
| Old Town Hall |
| Old Union Methodist Church |
| Ott's Chapel |
| Owl's Nest Country Place |
| Pagan Creek Dike |
| Palmer Home |
| Pepper, Carlton, David, Farm |
| Perry-Shockley House |
| Peterson and Mustard's Hermitage Farm |
| Pharo House |
| Philips-Thompson Buildings |
| Phillips Potato House |
| Pierson, T., Farm |
| Poinsett House |
| Point Farm |
| Ponder, Gov. James, House |
| Poplar Hall |
| Port Penn Historic District |
| Portsville Lighthouse |
| Postles House |
| Prince George's Chapel |
| Public School No. 111-C |
| Public School No. 19 |
| Pyle, Howard, Studios |
| Pyle, Joshua, House and Wagon Barn |
| Quaker Hill Historic District |
| Ralph Potato House |
| Rawley House |
| Raymond Neck Historic District |
Data from United States Park Service and Wikidata
