From NH to LA there is a blue line curving along what is close to the I95 I85/I10 I20 interstate corridor. Somewhat the same on the I% corridor on the west coast. As cities build on these interstates we are getting to what I call a linear megacity with little rural breaks between cities. When Dwight Eisenhower proposed the interstate highway system for defense reasons I’m pretty sure no one considered this consequence-a linear mega city-would arise. Probably affects weather patterns, voter patterns, social interactions, commerce etc. I haven’t seen a study on this but maybe my niece can do one as her economics thesis.
I% = I5 slow fingers this early.
In the Carolinas, that blue line roughly parallels I-95. It was there long before any urbanization occurred, back to the 18th century, really. It’s mostly small towns still, though some have more recently morphed into suburbs with the northern influx. It’s the old plantation belt, mostly rural and agricultural, but quite black. Some counties are over 50%.