Lake Dallas is a city in Denton County, Texas, United States. It is located in North Texas, northwest of the city of Dallas, on the shores of Lewis…Lake Dallas is a city in Denton County, Texas, United States. It is located in North Texas, northwest of the city of Dallas, on the shores of Lewisville Lake. The community's name derives from the original name of the lake. It is also one of the four communities in the Lake Cities.