 It is not included within the National Highway System.When originally designated in 1924, State Route 186 composed of the entirety of its current route, and the stretch of State Route 235 from the current northern terminus of State Route 186 in McComb to Hoytville.In 1937, State Route 186 was extended north along the current alignment of State Route 235 from Hoytville to that highway's current northern terminus at State Route 65 along the Maumee River northeast of Grand Rapids.