Delaware - Area of significance: Architecture
| Pyle, Joshua, House and Wagon Barn |
| Quaker Hill Historic District |
| Ralph Potato House |
| Rawley House |
| Raymond Neck Historic District |
| Reading, Philip, Tannery |
| Red Clay Creek Presbyterian Church |
| Redden Forest Lodge, Forester's House, and Stable |
| 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 |
| Robbins, David, Homestead |
| Robinson House |
| Robinson, Jesse, House |
| Rockland Historic District |
| Rockwood |
| Rodney Court |
| Rodney Square Historic District |
| Roosevelt Inlet Shipwreck |
| Rosedale |
| Rosemont |
| Ross, Edgar and Rachel, House |
| Ross, Gov. William H., House |
| Ross Point School |
| Rotheram Mill House |
| Rumsey Farm |
| Russell, William, House |
| Ruth Mansion House |
| Savin-Wilson House |
| Saxton United Methodist Church |
| Schagrin, Charles, Building |
| Schoonover, Frank E., Studios |
| Scott A.M.E. Zion Church |
| Scott's Store |
| Shallcross, Sereck, House |
| Shipley Run Historic District |
| Short Homestead |
| Short's Landing Hotel Complex |
| Sipple House |
| Sipple, Thomas, House |
| Smyrna Historic District |
| Snowland |
| South Milford Historic District |
| 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 |
| Starl House |
| Starr House |
| STATE OF PENNSYLVANIA (steamboat) |
| State Theater |
| Steel, James, House |
| Stevens, William, House |
| Stewart, James, House |
| Stewart, James, Jr., House |
| St. Georges Cemetery Caretaker's House |
| St. Georges Presbyterian Church |
| 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 Church |
| St. Joseph's Industrial School |
| St. Luke's Protestant Episcopal Church |
| St. Mary of the Immaculate Conception Church |
| St. Mary's School |
| St. Nicholas Ukrainian Catholic Church |
| Stockton-Montmorency |
| St. Paul's Episcopal Church |
| Strand Millas and Rock Spring |
| St. Stephen's P.E. Church |
| St. Thomas Episcopal Church |
| Stubbs, Elizabeth, House |
| Sudler House |
| Sussex County Courthouse and the Circle |
| Sussex National Bank of Seaford |
| Sutton, Thomas, House |
| Swanwyck |
| Talley, William, House |
| Tatnall, Joseph, House |
| Taylor's Bridge School |
| Teddy's Tavern |
| Tharp House |
| Thomas, David W., House |
| Thomas' Methodist Episcopal Chapel |
| Thorne, Parson, Mansion |
| Todd's Chapel |
| Town Point |
Data from United States Park Service and Wikidata
