After leaving Cambridge, US 12 passes through Oakland and crosses WIS 26, WIS 89, and WIS 106 in Fort Atkinson. WIS 89 joins US 12 as the route turns southward to approach Whitewater, bypassing the city to the south into Walworth County. The route briefly enters Rock County before crossing into Walworth County. WIS 89 turns off US 12 at its junction with WIS 59. WIS 59 East follows US 12 briefly before turning north into the city. US 12 passes through La Grange and turns south at the junction with WIS 20 to follow WIS 67 south. US 12 turns southeast off WIS 67 onto a freeway northeast of Elkhorn. The highway crosses over WIS 11 with no access (although access is provided via nearby I-43), then interchanges with I-43. Access for Lake Geneva is provided at WIS 120 and WIS 50 as US 12 passes the city to the east. The highway turns south into Genoa City, where the freeway ends and US 12 follows the crossroad into Illinois.
