Delaware - Role: Building
| Masonic Hall and Grand Theater |
| Mason, J., Farm |
| Maston House |
| Maull House |
| Mayfield |
| McClary House |
| McColley, James, House |
| McColley's Chapel |
| McCormack, J., Farm |
| McCoy House |
| McDaniel, Delaplane, House |
| McDaniel, J., Farm |
| McIntyre, J., Farm |
| McLane, Louis, House |
| McWhorter House |
| Meeteer House |
| Melson House |
| Memorial Hall |
| Merestone |
| Mermaid Tavern |
| Messick, Dr. John W., House and Office |
| Meteer Store House |
| Middletown Academy |
| Mifflin-Marim Agricultural Complex |
| Milford New Century Club |
| Milford Railroad Station |
| Milford Shipyard Area Historic District |
| Mill Creek Friends Meetinghouse |
| Mill House |
| Mispillion Lighthouse and Beacon Tower |
| Misty Vale |
| Mondamon Farm |
| Monterey |
| Montgomery House |
| Moore House |
| Moore Potato House |
| Mordington |
| Morgan, William, Farm |
| Morrow, James, House |
| Mount Cuba |
| Mount Lebanon Methodist Episcopal Church |
| Mount Pleasant |
| Mount Pleasant Methodist Episcopal Church and Parsonage |
| Naaman's Creek School |
| Naudain, Arnold S., House |
| Nelson, John B., House |
| Newark Opera House |
| Newark Passenger Station |
| Newark Union Church and Cemetery |
| New Castle County Court House |
| New Castle Leather Raw Stock Warehouse |
| New Century Club |
| Newport National Bank |
| Newport Railroad Station |
| Norwood House |
| Octagonal Schoolhouse |
| Okolona |
| Old Asbury Methodist Church |
| Old Brick Store |
| Old Bridgeville Fire House |
| Old Cann Mansion House |
| Old Christ Church |
| Old Customshouse |
| Old Drawyers Church |
| Old Fire House |
| Old First Presbyterian Church |
| Old First Presbyterian Church of Wilmington |
| Old Ford Dairy |
| Old Fort Church |
| Old Newark Comprehensive School |
| Old Post Ofice |
| Old St. Anne's Church |
| Old Statehouse |
| Old Stone Tavern |
| Old St. Paul's Methodist Episcopal Church |
| Old Sussex County Courthouse |
| Old Town Hall |
| Old Union Methodist Church |
| Ott's Chapel |
| Owl's Nest Country Place |
| Palmer Home |
| Parker's Dairy Palace |
| Penn Farm of the Trustees of the New Castle Common |
| Pepper, Carlton, David, Farm |
| Perry-Shockley House |
| Peterson and Mustard's Hermitage Farm |
| Pharo House |
| Philips-Thompson Buildings |
| Phillips Potato House |
| Phillips, Thomas, Mill Complex |
| Pierson, T., Farm |
| Poinsett House |
| Point Farm |
| Ponder, Gov. James, House |
| Poplar Hall |
| Portsville Lighthouse |
| Postles House |
| Prince George's Chapel |
| Prospect A.M.E. Church |
| Public School No. 111-C |
Data from United States Park Service and Wikidata
