Seattle City Light

Seattle's foray into electricity generation began with an opportunity - an existing dam at the Cedar River that could be used to generate power - and a need - cheap electricity to power street lights in a rapidly growing city.Although originally part of the water utility, voters amended the City Charter in 1910 to create the Lighting Department (popularly and now officially referred to as Seattle City Light). Under the leadership of Superintendent J.D. Ross, City Light built hydroelectric dams on the Skagit in the North Cascades. Both public and private power was supplied to Seattle until 1951 when the City purchased the private electrical power supply operations, making the Lighting Department the sole supplier. In the 1960's, City Light built the Boundary Dam in Northeast Washington that now generates over a third of the utility's power output. City Light remains the largest municipally-owned utility in the Pacific Northwest.

Power Generation: Introduction

Seattle City Light built, owns, and operates four major hydroelectric dams and powerhouses: Gorge, Diablo, and Ross, all on the Skagit River in the North Cascades, and Boundary on the Pend Oreille River in the northeastern corner of Washington. The utility also operates smaller generation facilities on the Cedar and Tolt Rivers and contracts for additional power from environmentally-friendly sources and the Bonneville Power Administration. City Light owns hundreds of miles of transmission right-of-way and infrastructure to deliver this electricity to Seattle.


Diablo Dam Spilling, 2003


Power Generation: Cedar Falls Plant

In 1902, Seattle voters approved a $590,000 bond issue to finance construction of a hydroelectric plant on the Cedar River. This facility began operation in 1905, powering the City's street light network.

Cedar River Power line and Powerhouse, 1922 Cedar Falls Powerhouse, 2000


Power Generation: Steam Plants

The Lake Union Steam Plant, completed in 1917, augmented City Light's electricity supply. The City acquired the Georgetown Steam Plant from Puget Sound Power & Light in 1951.

Lake Union auxiliary steam station, 1930


Power Generation: Skagit Project - Gorge Dam

City Light completed Gorge Dam, its first hydroelectric dam on the Skagit River, in 1924.The Gorge High Dam replaced the original dam in 1961.

Gorge railroad bridge, Gorge powerhouse at Newhalem, 1938 Gorge Dam spilling, 2002


Power Generation: Skagit Project - Diablo Dam

Diablo Dam was completed in 1930 and began generating electricity in 1936.

Diablo Dam, 2002

Diablo Dam & Diablo Lake, Ruby Mountain in background, 1935


Power Generation:Skagit Project - Diablo Dam Workers

Diablo Dam workers on incline, 1928


Power Generation: Skagit Project - Ross Dam

Ross Dam and Powerhouse, 2002


Power Generation: Skagit Project - Workers

View of Camp, Skagit River, mountains, and railroad, 1930 Gorge lunchroom, 1935


Power Generation: Skagit Project - Tourism

Crowd on train between Rockport and Camp, 1931 The Alice Ross on Diablo Lake, 1936


Power Generation: Boundary Project

In 1967, City Light finished construction of the Boundary Dam on the Pend Orielle River in Northeast Washington near the Canadian and Idaho borders.

Boundary Dam Construction, 1966 Generating Turbine, 1999


Boundary Dam Spilling, 1999