 The primary freeway running through Lewisville is Interstate 35E, which runs north–south through the city.Before it was built, US Highway 77 (now Mill Street) was the main through route, connecting the city with Denton to the north and Dallas to the south.In 1998, the Texas Department of Transportation carried out a Major Investment Study to examine the possibility of expanding the section of Interstate 35E between Interstate 635 and U.S. Route 380, the primary focus being an  stretch from Texas State Highway 121 to the bridge crossing Lewisville Lake.