It was (sort of still is) an early major east-west route. Late 20's I believe and somewhat more used for goods transport. Went souther as you got wester. You could travel America (US) and see most all of it without leaving the road. You could meet & talk to people, sit on an actual gas station porch and philosophize with townsfolk. On modern roads you go fast but only see 25 feet of landscaping. See Compare them.

I don't know there were so many songs...the best known was written for the bland TV show. I drove both some distance in the late 50's. We didn't really have the I-road system yet. Lincoln Highway was just bits & pieces by then and not so interesting. But my parents drove it all in the 20's and had a lifetime's adventures. So in people's thoughts by the 50's & 60's, Rte 66 was the much better known road and still a major east-west route. I liked it, too.