I remember reading an article that describe borders, especially borders along rivers, as going through an almost expected transformation. The Rhine River was originally a border between the Romans and the Germanic tribes. Eventually the Rhine River became a highway central to the German culture and industry of modern times. If the Rio Grande was once a highway, it is now a river where a Tex-Mex culture is growing, where on the differing sides of the border people speak both languages and given time may find themselves having more in common with one another than either D.C. or Mexico City. Rivers may begin as boundaries but always become cultural highways.