Grand Coulee Dam is the principal feature of the Columbia Basin Project in central Washington State. Completed in 1942, the dam is among the largest concrete structures ever constructed. When the dam was built, it was constructed with two powerplants, one at each end of the 3,800 foot long dam, which contain nine generating units each. Between 1967 and 1974, a third powerplant containing six generating units was constructed. The power generated at Grand Coulee supplies a large portion of the power needed in the Pacific Northwest. The third powerplant alone provides enough electricity to meet the power needs of the cities of Portland and Seattle.