Delaware - Significance region: Local
| Jackson-Wilson House |
| Johnson Home Farm |
| Johnson-Morris House |
| Jones, Enoch, House |
| Justis-Jones House |
| Justis, Thomas, House |
| KATHERINE M. LEE (Schooner) |
| Keil, Max, Building |
| Keil, Max, Building |
| Kenton Historic District |
| Kenton Post Office |
| Kerr, Andrew, House |
| Killgore Hall |
| Killgore, Joseph, House |
| Kingswood Methodist Episcopal Church |
| La Grange |
| Lamb, Thomas, Farm |
| Lamb, Thomas, House |
| Laurel Historic District |
| Laws, Alexander, House |
| Lesley-Travers Mansion |
| Lewden, John, House |
| Lewes Historic District |
| Lewes Presbyterian Church |
| Lewis Family Tenant Agricultural Complex |
| Lewis, Jefferson, House |
| Liedlich, Charles and Edith, House |
| Lindale,John B.,House |
| Lindsay, J., Barn |
| Lindsey, Samuel, House |
| Liston House |
| Liston Range Front Lighthouse |
| Little Creek Methodist Church |
| Lobdell Estate, Minquadale Home |
| Logan House |
| Lore, Charles B., Elementary School |
| Lower Market Street Historic District |
| Lum's Mill House |
| Macomb Farm |
| MAGGIE S. MYERS (schooner) |
| Maple Grove Farm |
| Maples |
| Marshallton United Methodist Church |
| Marsh, Peter, House |
| Masonic Hall and Grand Theater |
| Mason, J., Farm |
| Maull House |
| Mayfield |
| McClary House |
| McColley's Chapel |
| McCormack, J., Farm |
| McDaniel, Delaplane, House |
| McDaniel, J., Farm |
| McIntyre, J., Farm |
| McWhorter House |
| Meeteer House |
| Melson House |
| Memorial Hall |
| Merestone |
| Mermaid Tavern |
| Messick, Dr. John W., House and Office |
| Meteer Store House |
| Middletown Academy |
| Middletown Historic District |
| Mifflin-Marim Agricultural Complex |
| Mill Creek Friends Meetinghouse |
| Mill House |
| Milton Historic District |
| Mispillion Lighthouse and Beacon Tower |
| Misty Vale |
| Mondamon Farm |
| Montchanin Historic District |
| Montgomery House |
| Moore House |
| Moore Potato House |
| Mordington |
| Morgan, William, Farm |
| Morrow, James, House |
| 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 |
| Newark Union Church and Cemetery |
| New Castle Leather Raw Stock Warehouse |
| Newport National Bank |
| Newport Railroad Station |
| Norwood House |
| Noxontown |
| Okolona |
| Old Asbury Methodist Church |
| Old Bridgeville Fire House |
| Old Fire House |
| Old First Presbyterian Church |
| Old First Presbyterian Church of Wilmington |
Data from United States Park Service and Wikidata
