Without a doubt, the Interstate system has interrupted its smooth flow by a bunch, but not much before the Interstate cut it up, the cities along its path had already disrupted its smooth flow a lot. Our family drove from just west of Chicago to LA on Rt 66 in Dec of 1965, and then again in Dec of 1971. The 71 trip already had parts of the original highway bypassed. I believe the entire route was 4 lane shortly after our 71 trip.
Not much love for touristy stuff in Missouri on that map. If it was printed today, Johnny Morris would be the main sponsor!
Now you go through saint looey Joplin, Missouri, And Oklahoma city is mighty pretty. You see amarillo, Gallup, New Mexico, Flagstaff, Arizona. Don't forget Winona, Kingman, Barstow, san Bernandino. Won't you get hip to this timely tip When you make that California trip Get your kicks on route sixty-six.