Washington's Grand COULEE Dam is a large hydroelectric dam located on the Columbia River in Washington State. It was constructed between 1933 and 1942 and is the largest concrete structure in the United States. The dam provides irrigation water for over 670, 000 acres of farmland and generates enough electricity to power over three million homes. It is also a major tourist attraction, with visitors coming from all over the world to see the dam and its surrounding area.