I have a theory that newer borders more rectangular, whereas older borders follow natural wiggly features like rivers, similar to newer cities' roads being more

I have a theory that newer borders more rectangular, whereas older borders follow natural wiggly features like rivers, similar to newer cities' roads being more rectangular, whereas older roads are more higgly-piggly organic. The older ones grew; the newer were planned. You can see it east-to-west in the USA states' borders.