US 40 and US 50 both connected Kansas City and St. Louis. US 40 took a more northerly route through Columbia, while US 50 went through Jefferson City. The 1927 Missouri official road map combined the two routes on this route map. Before 1926, US 40 was State Highway 2; US 50 was State Highway 12. While US 40 still exists, its modern equivalent is Interstate 70.
Also note a separate "Gravel" route between Columbia and Fulton and again between Fulton and Calwood. US 40 traffic may have been routed on these roads for a period of time until the main route was upgraded to concrete construction. Most of that work appeared to have been completed by 1927, except for a few segments in Callaway County, listed as "Concrete Under Contract".
This image was scanned at 150 dpi.