The answer is easy, when you know it. Because he made the Missouri himself. What we now know as the Missouri River was made of other rivers that the big ice sheet turned around as it advanced and of the water from the ice as the glacier melted its way back home. It was something like Mary and the little lamb, all the time, so long as Mr. Keewatin travelled south; for everywhere he went the Missouri was sure to go, because he kept pushing it ahead of him.
HOW THE OLD MEN PUSHED THE MISSISSIPPI ABOUT
As the ice sheets pushed into its valleys, now from the northeast and now from the northwest, the Mississippi River was pushed back and forth as if it were a—well, as if it weren't anything! It is known that the Mississippi was pushed out of bed by this burly guest from the north because its former channels have been traced along the old ice fronts.
In one part of its course the Mississippi actually got misplaced, and hasn't found its way back to its old bed to this day. This you can see at Fort Snelling, Minnesota. At that point the Minnesota River flows in the Mississippi's old valley—which is plainly too big for it—while above Fort Snelling the Mississippi is forced to squeeze its way through a stingy little gorge that used to belong to the Minnesota, and I'm sure would be plenty big enough for it now. It's like the story of a changeling baby in a fairy tale, isn't it? Only in the fairy tale the changeling always gets back to his old home, while the misplaced Mississippi in Minnesota doesn't.
But the glaciers made it up to the Mississippi, in a way, for this rude jostling. They not only left it an enormous extra supply of water as they melted back home—what would a river be without water?—but they actually took some smaller rivers away from the St. Lawrence and made them do their pouring into the Mississippi system. Although they didn't owe the Ohio any apology for anything, so far as I know, they did the same thing for it, just to be good fellows, I suppose. All the rivers that now empty into the Ohio above Cincinnati used to flow into Lake Erie, but the glaciers turned them south and they've gone on obediently flowing that way ever since.
A PLOWMAN WHO PLOWED THE FARMS AWAY
That these giants of the north, although they must have looked as cold as ice, really had good hearts is shown by the way Old Mr. Labrador treated New England when he went Down East. New England was at that time covered with good, deep, rich soil, the decay of the granite rocks that had been basking in the sun for ages and growing early grass and vegetables for the live stock of those days. Then along came Old Mr. Labrador with his plow, and set to work. But he plowed so deep that he plowed all the farms away! Of the gigantic furrows that he turned a lot of the slices fell over into New York State; but some, I'm sorry to say, dropped off into the sea. This left New England in a bad way, so far as prizes for farm produce at the country fairs a few thousand years later were concerned.
But then what do you suppose Mr. Labrador did, the good old soul? He took a lot of streams that had been flowing north, blocked them up with pebbles and dirt, making them turn right around and flow south, so that in climbing down from the rocks in these new unworn beds they made waterfalls. And it was from the power made by its waterfalls, you know, as your geography tells you, that New England grew to be a great "manu-factur-ing" section.
Courtesy of "The Scientific American."