Delaware - Significance region: Local
| Old Ford Dairy |
| Old Fort Church |
| Old Newark Comprehensive School |
| Old Stone Tavern |
| Old Town Hall Commercial Historic District |
| Old Union Methodist Church |
| Ott's Chapel |
| Palmer Home |
| Parker's Dairy Palace |
| Pepper, Carlton, David, Farm |
| Perry-Shockley House |
| Pharo House |
| Philips-Thompson Buildings |
| Phillips Potato House |
| Phillips, Thomas, Mill Complex |
| Pierson, T., Farm |
| Pine Grove Furnace Site |
| Poinsett House |
| Poplar Hall |
| Port Mahon Lighthouse |
| Port Penn Historic District |
| Portsville Lighthouse |
| Postles House |
| Prospect A.M.E. Church |
| Public School No. 19 |
| Public School No. 29 |
| Pyle, Joshua, House and Wagon Barn |
| Quaker Hill Historic District |
| Ralph Potato House |
| Rawley House |
| Red Clay Creek Presbyterian Church |
| Reed House |
| Reed, Jehu, House |
| Retirement Farm |
| Reynold's Candy Company Building |
| Rhodes Pharmacy |
| Ricards House-Linden Hall |
| Richards Historic District |
| Richards Mansion |
| Rider Potato House |
| Riverdale |
| Riverview Cemetery Company of Wilmington, Delaware |
| Robbins, David, Homestead |
| Robinson, Jesse, House |
| Rockford Park |
| Rodney Court |
| Rodney Square Historic District |
| Rosedale |
| Rosemont |
| Ross, Edgar and Rachel, House |
| Ross Point School |
| Rumsey Farm |
| Russell, William, House |
| Ruth Mansion House |
| Savin-Wilson House |
| Saxton United Methodist Church |
| Schagrin, Charles, Building |
| Scott A.M.E. Zion Church |
| Scott's Store |
| Seaford Station Complex |
| Shallcross, Sereck, House |
| Shipley Run Historic District |
| Short Homestead |
| Short's Landing Hotel Complex |
| Sipple House |
| Sipple, Thomas, House |
| Snowland |
| Spring Banke |
| Springer, Charles, Tavern |
| Springer-Cranston House |
| Springer Farm |
| Spring Garden |
| Stanley Potato House |
| St. Anthony's Roman Catholic Church |
| Star Hill AME Church |
| Starr House |
| STATE OF PENNSYLVANIA (steamboat) |
| Steel, James, House |
| Stevens, William, House |
| Stewart, James, Jr., House |
| St. George's Chapel |
| St. Hedwig's Roman Catholic Church |
| Stinson, J., Farm |
| St. James Church |
| St. John's Methodist Church |
| St. John the Baptist Roman Catholic Church |
| St. Joseph's Catholic Church |
| St. Joseph's Church |
| St. Joseph's Industrial School |
| St. Joseph's on the Brandywine |
| St. Mary of the Immaculate Conception Church |
| St. Nicholas Ukrainian Catholic Church |
| St. Paul A.M.E. Church |
| Strand Millas and Rock Spring |
| St. Stephen's P.E. Church |
| St. Thomas Episcopal Church |
| Stubbs, Elizabeth, House |
| Sudler House |
| Sussex National Bank of Seaford |
| Sutton House |
Data from United States Park Service and Wikidata
