K-18 is a 206-mile (332 km), west–east state highway in the U.S. State of Kansas. K-18's western terminus is at U.S. Route 24 (US-24) near Bogue and the eastern terminus is at K-99 south of Wamego. Portions of the highway have been upgraded to a freeway beginning in 2012.
^Rand McNally and Company (1926). "Kansas" (Map). Rand McNally Auto Road Atlas of the United States, including a Brief Description of the National Parks and Monuments. Chicago: Rand McNally and Company. pp. 56–57.