| Leavenworth Fruit | Leavenworth | WA |
| Lehigh Portland Cement | Metaline Falls | WA |
| Lents | Bremerton | WA |
| Lewiston-Clarkston Improvement | Clarkston | WA |
| L.G. Massart | Seattle | WA |
| L.H. Bates Vocational Technical Institute | Tacoma | WA |
| Libby's (Libby, McNeill & Libby) | Walla Walla | WA |
| Lincoln High School | Seattle | WA |
| Linde Air Products | Spokane | WA |
| Lipsee | Tacoma | WA |
| Liquid Air | Kent | WA |
| Liquid Carbonic | Seattle | WA |
| Liscomb Bay | Vancouver | WA |
| Little Falls Fire Clay | Bayne | WA |
| Little Goose Lock & Dam | Ayer | WA |
| Litwin | Everett | WA |
| Lnts P&H, Office Building & Cafeteria | Kent | WA |
| Lockheed Shipbuilding and Construction | Seattle | WA |
| Lone Star Industries | Seattle | WA |
| Long Bell | Longview | WA |
| Long Bell Power Plant | Longview | WA |
| Longfellow Elementary School | Spokane | WA |
| Longview Fiber | Seattle | WA |
| Longview Fiber | Longview | WA |
| Lower Columbia Cooperative Association | Grays River | WA |
| LPD #9 | Seattle | WA |
| Lucky Lager Brewing | Vancouver | WA |
| Luke School | Seattle | WA |
| Lunga Point | Vancouver | WA |
| Mackall Paine Veneer | Vancouver | WA |
| Madigan Army Hospital | Tacoma | WA |
| Madrona Elementary School | Seattle | WA |
| Maintenance Center | Olympia | WA |
| Manila Bay | Vancouver | WA |
| Manley-Moore Lumber | Fairfax | WA |
| Mannette Theatre | Bremerton | WA |
| Maple Elementary School | Seattle | WA |
| Marine Power & Equipment | Seattle | WA |
| Marsh Company Murray | Riverside | WA |
| Martinac Shipbuilding | Tacoma | WA |
| Martin-Close-Massart | Seattle | WA |
| Maywood Elementary School | Issaquah | WA |
| Maywood High School | Issaquah | WA |
| Maywood Junior High School | Issaquah | WA |
| McNally | Naches | WA |
| Meany J.High School | Seattle | WA |
| Medical Dental Building | Everett | WA |
| Mercer J.High School | Seattle | WA |
| Mercy Twin Theater | Union Gap | WA |
| Meridian Elementary | Kent | WA |
