| North Pacific Paper | Longview | WA |
| North Shore Boat Works | Vancouver | WA |
| Northwest Agri Products | Moses Lake | WA |
| Northwest Building Materials | Spokane | WA |
| Northwest Chair | Tacoma | WA |
| Northwestern Gas & Electric | Walla Walla | WA |
| Northwestern Improvement | Ravensdale | WA |
| Northwestern Improvement | Roslyn | WA |
| Northwestern Improvement | Cle Elum | WA |
| Northwestern Improvement | Ronald | WA |
| Northwestern Improvement | Tacoma | WA |
| North Western Lumber | Hoquiam | WA |
| Northwest Hospital | Seattle | WA |
| Northwest Improvement | Roslyn | WA |
| Northwest Light & Water | Yakima | WA |
| Northwest Marine Fiberglass | Seattle | WA |
| Northwest Natural Gas | Camas | WA |
| Northwestn Glass | Seattle | WA |
| Northwest Petrochemical | Anacortes | WA |
| Northwest Steel Rolling Mills | Seattle | WA |
| N River Senior High | Cosmopolis | WA |
| OCF | Tukwila | WA |
| O. Cohen Restaurant | Seattle | WA |
| Office Building - 4001 Sixth Avenue | Seattle | WA |
| Oklahoma | Bremerton | WA |
| Old Mines Building | Seattle | WA |
| Olympia Brewing | Olympia | WA |
| Olympia Christian School | Olympia | WA |
| Olympia Parking Garages | Olympia | WA |
| Olympic Calpet Refining | Seattle | WA |
| Olympic Forest Products | Port Angeles | WA |
| Olympic Hotel | Seattle | WA |
| Olympic View Middle School | Mukilteo | WA |
| Onalaska Lumber | Onalaska | WA |
| One Stadium Way Condominium Tower | Tacoma | WA |
| Oregon Washington Depot | Spokane | WA |
| Oregon-Washington Railroad & Navigation | Seattle | WA |
| Oregon-Washington Railroad & Navigation | Spokane | WA |
| Oroville Lumber | Oroville | WA |
| Orthopedic Hospital | Seattle | WA |
| Owens Corning | Spokane | WA |
| Owens Corning | Renton | WA |
| Owens Corning | Seattle | WA |
| Paccar Defense Systems | Renton | WA |
| Pacific Brotherhood Investment | Seattle | WA |
| Pacific Car & Foundry | Renton | WA |
| Pacific Coast | Seattle | WA |
| Pacific Coast Condensed Milk | Chehalis | WA |
| Pacific Coast Condensed Milk | Mount Vernon | WA |
| Pacific Coast Condensed Milk | Seattle | WA |
