Photo courtesy of David Backlin (taken July 2004)
US 71 used to go through the Bates County city of Adrian. It now bypasses the city, but the highway name lives on at this intersection with Missouri 18 as Old US 71 Highway. It's also an expression of a linguistic quirk present in the Kansas City area and other parts of western Missouri. Instead of saying "Highway 71", the common term is "71 Highway". I have read research papers that claim this is one of the few distinguishing characteristics of English as spoken in the Kansas City area.
Also note the destination sign for Merwin, a small town 13 miles west of Adrian on Missouri 18.