Delaware - Criteria: C (architecture/engineering)
| Grier House |
| Griffith's Chapel |
| Grose, Robert, House |
| Gyles, Stella Pepper, House |
| Hale-Byrnes House |
| Hall, Col. David, House |
| Hanson, B. F., House |
| Harlan and Hollingsworth Office Building |
| Hart House |
| Hazel Glen |
| Head of Christiana United Presbyterian Church |
| Hearn Potato House |
| Hebron Methodist Protestant Church and Cemetery |
| Hedgelawn |
| Hermitage, The |
| Hersey-Duncan House |
| Hicklen, William, House |
| Hickman Row |
| Higgins, S., Farm |
| Hill Island Farm |
| Hill, Robert, House |
| Hitch, E. L., Potato House |
| Hockessin Friends Meetinghouse |
| Hoffecker-Lockwood House |
| Holladay-Harrington House |
| Holly Oak |
| Holton, S., Farm |
| Holy Trinity |
| Homestead Hall |
| Hopkins' Covered Bridge Farm |
| Hudson, Alfred L., House |
| Huguenot House |
| Idalia Manor |
| Iron Hill School No. 112C |
| Ivyside Farm |
| Jackson-Wilson House |
| Johnson Home Farm |
| Johnson-Morris House |
| Jones, Enoch, House |
| Judge's House and Law Office |
| 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 |
| Lawrence |
| 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 |
| Linden Hill |
| Lindsay, J., Barn |
| Lindsey, Samuel, House |
| Liston House |
| Liston Range Front Lighthouse |
| Liston Range Rear Light Station |
| Little Creek Hundred Rural Historic District |
| Little Creek Methodist Church |
| Lobdell Estate, Minquadale Home |
| Lofland, Peter, House |
| Logan House |
| Lombardy Hall |
| Loockerman Hall |
| Lore, Charles B., Elementary School |
| Louviers |
| Lowber, Matthew, House |
| Lower Louviers and Chicken Alley |
| Lower Market Street Historic District |
| Lum's Mill House |
| MAGGIE S. MYERS (schooner) |
| Main Office of the New Castle Leather Company |
| Maple Grove Farm |
| Maples |
| Marcus Hook Range Rear Light |
| Marshallton United Methodist Church |
| Marsh, Peter, House |
| Masonic Hall and Grand Theater |
| Mason, J., Farm |
| Maston House |
| Maull House |
| Mayfield |
| McClary House |
| McColley, James, House |
| McColley's Chapel |
| McCormack, J., Farm |
Data from United States Park Service and Wikidata
