Rivers, mountain ranges, oceans, etc. Those are considered "natural boundaries".
Im just going to guess that its a boundary that nature provided, but and example is an ocean, a river, and a mountain.
The sea.
Nature has provided the Pyrenees Mountains as the boundary between France and Spain.
it is china and mongolia russia and spain japan and france australia to california now that is some examples of a political and a natural boundary
The Mississippi River was the natural boundary of the Louisiana Purchase on the east.
Mississippi
Mississippi River and Rocky Mountains.
Mississippi
The Mississippi River.
The Mississippi River is the East boundary for Arkansas.
The east was bounded by the Mississippi and the West ( andSouth) by the Missouri River.
The Mississippi River formed the western boundary.
Mississippi River
The Mississippi river was the border.
The Alps mountain range forms a natural boundary between France and Italy.
Tennessee is separated from Arkansas by the Mississippi River.