Camas
Crown Zellerbach Corp.

Everett
Everett Light & Power

Everett
Everett Railway & Electric Co.

Newhalem
Skagit River Railway

Renton
Puget Sound Electric Railway

Seattle
Pacific Northwest Traction

Seattle
Seattle Municipal Street Railway
An entire collection from SMSR is here

Seattle
Seattle, Columbia & Renton

Seattle
Seattle Waterfront Streetcar

Seattle
Seattle Monorail

Spokane
Spokane & Inland Empire RR

Spokane
Spokane Interurban Terminal

Spokane
Spokane, Coeur d'Alene and Palouse

Spokane
Washington Water Power Co.

Tacoma
Tacoma Municipal Railway

Vancouver
Clark County Transportation Co.

Walla Walla Valley
A website on this railroad is here

Yakima Valley Transportation Co.