Grand Coulee Dam is one of the largest concrete structures ever built.

It contains about twelve million cubic yards of concrete, which is enough to build a standard 16 foot wide highway from Seattle to New York City to Houston to San Diego and then back to Seattle.

The dam is 5,228 feet long and 550 feet high. Below is a timeline showing the construction and development history of the dam and its related facilities.


Work on the dam begins.


Congress authorizes development of Grand Coulee Dam and the Columbia Basin Project.


Grand Coulee Dam is essentially complete. The Left Power Plant begins to operate and power generation is immediately used to support the energy intensive needs of World War II. The foundations are complete for the Right Power Plant and Pumping Plant.


With the closing of the gates, the waters behind the dam rise 380 feet. The reservoir (called Franklin D. Roosevelt or Lake Roosevelt for short) extends 150 miles north, and provides over 630 miles of shoreline.


Construction of Grand Coulee Pumping Plant, which pumps water from Lake Roosevelt to Banks Lake to support irrigation, begins.


Six 65,000-horsepower pumps are installed to meet initial irrigation needs.


The last of eighteen, 108,000-kilowatt units is installed and the Left and Right Power Plants are considered complete.


Banks Lake is filled, delivering the first irrigation water.


Construction of the Third Power Plant begins.


The first of six units in the third power plant begins generating electricity.


The sixth unit for the Third Power Plant becomes operational, completing a 13 year project that increased the amount of power generation capacity by 3,900,000 kilowatts.

For further information, visit the Grand Coulee Dam website and the Operations page of this website.