Here are scanned images of the 1926 Official Highway Map from Missouri. It is the first printing since the US Highway numbering system became official. The original sheet was 23 3/8" x 19 3/8" so the full size images will be quite large. Click on the thumbnails at your own risk.
The first image is from the front of the map showing the main road network. The roads were added to a map showing the railroad system. Full size scan is 2805x2322 pixels at 120 pixels/in resolution.
The second image is from the back of the map. It shows the Kansas City and St. Louis insets, strip maps of the new US routes noting the former state designations, standard road signs as used in 1926, and several photographs taken around the state. Full size scan is 2805x2340 pixels at 120 pixels/in resolution.