U.S. Federal Route 18 runs east-west across Cerro Gordo County. This is a two-lane highway from the Cerro Gordo/Hancock County line to Interstate 35, near Clear Lake. From near Clear Lake it runs on a expressway to the Cerro Gordo/Floyd County Line. U.S. Rt 18 passes through the following towns in Cerro Gordo County. Ventura Clear Lake U.S. Rt. 18 is multi-plexed in Cerro Gordo County. BUSN Loop I-35, near Clear Lake. Interstate 35, near Clear Lake.
Iowa State Route 27, from near Clear Lake to the Cerro Gordo/Floyd County Line.
Branches of U.S. Rt. 18 in Cerro Gordo County. A BGS on SB I-35/IA St Rt 27. SB BUSN Loop I-35/WB U.S. Rt. 18, west of I-35. A junction marker on WB BUSN U.S. Rt. 18/IA St Rt 122. A BGS on SB I-35; EB U.S. Rt. 18; SB IA St Rt 27. SB I-35; EB U.S. Rt. 18; SB IA St Rt 27 near Mason City. EB U.S. Rt. 18/SB IA St Rt 27 at the interchange with I-35. This is a incomplete interchange. It is set for a westward extention of the expressway. EB U.S. Rt. 18/SB IA St Rt 27 on the future colector/distributor lanes for the interchange with I-35. EB U.S. Rt. 18/SB IA St Rt 27 south of Mason City. EB U.S. Rt. 18/SB IA St Rt 27 southeast of Mason City.