 The route between Mondovi and Humbird was not numbered until the early 1920s, when Highway 18 was extended west from Humbird past Mondovi to Prescott, eliminating Highway 34.When US 10 was designated in late 1926, it ran along U.S. Highway 12 from Minnesota east to Humbird, splitting there to run to Manitowoc.The piece of former Highway 18 west of Humbird became Highway 34, as the number 18 conflicted with U.S. Highway 18.