Lewisville is a city in the U.S. state of Texas, located in Denton County with portions extending into Dallas County. As one of the Mid-Cities …Lewisville is a city in the U.S. state of Texas, located in Denton County with portions extending into Dallas County. As one of the Mid-Cities within the Dallas–Fort Worth metroplex, the 2020 census reported a population of 111,822.