Constructed between 1946 and 1954, J. Strom Thurmond Dam was the first hydropower project built on the Savannah River. Behind it lies one of the largest Corps of Engineer lakes east of the Mississippi. The powerhouse contains seven power units, each capable of generating 40,000 kilowatts, and its average annual energy output is 920-million kilowatt hours. Since its completion, the dam has prevented millions of dollars in flood damage to downstream sites and produced power revenues sufficient to repay its original construction cost in less than 25 years.