| Seattle Steam | Seattle | WA |
| Seattle Supply | Seattle | WA |
| Seattle Tacoma International Airport | Seattle | WA |
| Seattle Tacoma Power | Seattle | WA |
| Seattle Tacoma Satellite Transit System | Seattle | WA |
| Seattle Tacoma Shipbuilding | Seattle | WA |
| Seattle Tennis Club | Seattle | WA |
| Seattle Terminal | Seattle | WA |
| Seattle Trust | Seattle | WA |
| Seattle University | Seattle | WA |
| S.E. Brown & Company | Seattle | WA |
| Second Bank Of Commerce | Seattle | WA |
| Securities Building | Seattle | WA |
| Self Parking Facility | Seattle | WA |
| Sewage Plant | Lynnwood | WA |
| Seward Elementary School | Seattle | WA |
| Shell | Anacortes | WA |
| Shell | Spokane | WA |
| Shell | Seattle | WA |
| Shelton Mill | Shelton | WA |
| Shepherd Fruit Products | Wenatchee | WA |
| Sheraton Hotel | Spokane | WA |
| Sherman Elementary School | Tacoma | WA |
| Sherwood Inn | Tacoma | WA |
| Shoreline Community College | Seattle | WA |
| Shore Line Junior High School | Seattle | WA |
| Siboney | Tacoma | WA |
| Sicily | Tacoma | WA |
| Sick's Rainier Brewing | Seattle | WA |
| Siems Carey H.S. Kerbaugh | Port Angeles | WA |
| Siems Drake Puget Sound | Seattle | WA |
| Sierra Pacific Industries | Aberdeen | WA |
| Sigma Alpha Epsilon | Pullman | WA |
| Simpson Insulation Board | Shelton | WA |
| Simpson Logging | Shelton | WA |
| Simpson Paper | Tacoma | WA |
| Simpson Paper | Everett | WA |
| Simpson Tacoma Kraft | Tacoma | WA |
| Simpson Timber | Shelton | WA |
| Sisters Of Providence | Issaquah | WA |
| Sisters Of Saint Joseph | Bellingham | WA |
| Sitka Pulp Mill Builders | Seattle | WA |
| Skagit County Dairymen's Association | Mount Vernon | WA |
| Skyline Apartment Building | Seattle | WA |
| Slems Drake Puget Sound | Seattle | WA |
| Snoqualmie Falls Lumber | Snoqualmie Falls | WA |
| Snoqualmie Falls Power | Tacoma | WA |
| Socony Mobil Oil | Ferndale | WA |
| Sodo | Seattle | WA |
| Solomon | Vancouver | WA |
