Grand Coulee Dam is a gravity dam on the Columbia River built to produce hydroelectric power and provide irrigation. It was constructed between 1933 and 1942, originally with two power plants. A third power station was completed in 1974 to increase its energy production. It is the largest electric power-producing facility in the United States. The completed dam is now almost a mile long at 4,300 ft (1,300 m). I link to Good Fences each weekend although this picture doesn't seem to have a fence!