After several miles, the highway enters the state of Kentucky and crosses I-65 again, where it passes through Franklin and intersects KY 100. From here, the highway is known as Bowling Green Road (Nashville Road) once it enters Warren County, and passes through fields, as well as giving access to the town of Woodburn. Entering the city of Bowling Green, the route intersects the William H. Natcher Parkway as well as US 231 as the route passes east of downtown Bowling Green. On the eastern side of town, Louisville Road carries US 31W, US 68, and KY 80 east and then northeast, where US 68 and KY 80 split off to the east. US 31W passes within on an entrance to Mammoth Cave National Park near Park City, after crossing I-65 again, this time without direct access to the freeway. The highway travels through Cave City as Duke Highway while crossing two major state routes, KY 90, and then KY 70.