Waterton-Glacier International Peace Park like other land areas around the world, has both political and natural boundaries. One difference between the two is that political boundaries are established by humans. The designation of political boundaries can be very controversial, take many years to make, and can change with wars and conflicts. As you step over a political boundary in one direction or the other on the land, the rules of behavior change. For an animal or plant stepping over the political boundary, life also changes. On one side they can be hunted, for instance, and on the other they are protected. The difference between humans and other species, of course, is that we know about the rules (or can find them out) that accompany political boundaries and other species don't.
Natural boundaries, on the other hand, are things like watersheds, rivers, divides and landscape changes from one type of land to another. These create barriers to further travel for many species. A West slope cutthroat can swim toward the Continental Divide from the Pacific, but may be prevented from getting to the Divide by waterfalls or dams which create barriers or "boundaries" along the way. Every species' boundaries are different. A fish's boundary is the edge of the water, but a bear can ignore that boundary. A bird can cross boundaries that would hinder a fish or a bear. Humans are continually stretching our "boundaries" and have extended them all the way to the moon!
As the above indicates, another major difference between political boundaries and natural boundaries is that the natural boundaries are usually an obstacle to travel and/or noticeably different from one side to the other. Whereas political boundaries often are plotted in straight lines across a landscape and ignore the natural boundaries (but not always) so even people would not recognize it as a boundary if there were no signs. Look at a map that shows the boundaries for Waterton-Glacier International Peace Park. Which parts of the park boundary follow natural features and which ones don't?
One unique natural boundary that occurs in the park is Triple Divide Peak. It is a mountain about ten miles south of St. Mary in Glacier National Park. As you may have guessed from its name, this mountain is a three-way divide. Rainwater falling on the east side of the mountain flows into Atlantic Creek, which eventually goes to the Missouri-Mississippi river system and into the Atlantic Ocean. Water falling on the west side flows into Pacific Creek and eventually the Pacific Ocean. Rain on the north side flows into Hudson Bay Creek and, you guessed it, eventually to Hudson Bay.