Lewisville Lake, formerly known as Garza-Little Elm Reservoir, is a reservoir in North Texas (USA) on the Elm Fork of the Trinity River in Denton County near Lewisville. Originally engineered in 1927 as Lake Dallas, the reservoir was expanded in the 1940s and 1950s and renamed Lewisville Lake. It was built for flood control purposes and to serve as a water source for Dallas and its suburbs, but residents also use it for recreational purposes.