Look closely (in Google maps) at the state borders between Louisiana and Mississippi and Arkansas. Originally they followed the Mississippi River. The river now follows a very different course. It has moved around <b>alot</b> in the past 200 years. Nothing as dramatic as switching to the Atchafalaya River, but caused by same natural forces that make it want to move again.,(reply>), @Liggliluff the Mississippi’s channel has changed many, many times. All up and down the river are little bits and nibs of land that were on one side when the states were created and are now on the other side, cut off from the rest of their state.,(reply>), It happens a lot when you define the border according to how the river was at that point. Europe have a lot of borders that follow rivers. A few do no longer follow the rivers; but most are still on the rivers (assuming they keep these updated, or that the river haven't moved since these lines were drawn, where some might have been drawn after the world wars).<br>Poland–Germany follows the river, so does Germany–France, Slovakia–Hungary, Bosnia–Serbia, Croatia–Bosnia, Serbia–Romania, Bulgaria–Romania, Greece–Turkey. – But then you have Slovenia–Croatia, Croatia–Serbia, Belarus–Ukraine that does not follow the river no more.