, August 2013 Montana's secondary system was established in 1942, but secondary highways (S routes) were not signed until the 1960s. and are abbreviated as "S-nnn". Route numbers 201 and higher are, with very few exceptions, exclusively reserved for S routes. Notable exceptions include,
MT 287, and the former MT 789. The highway markers for Montana's Secondary Highways are distinctive in that the route number appears in black on a white down-pointing
arrowhead. (Early markers were white numbers on black arrowheads with the word Montana in the flat top of the inverted arrowhead and Secondary appearing below the route number on the shields.) ==See also==