continental divide

Continental divides are clearly definable lines, usually running along the ridgetops of mountain chains, that separate one drainage basin from another. In a journal entry dated August 12, 1805, Meriwether Lewis writes: “After refreshing ourselves we proceeded on to the top of the dividing ridge from which I discovered immence ranges of high mountains still to the West of us with their tops partially covered with snow. I now decended the mountain about of a mile which I found much steeper than on the opposite side, to a handsome bold running Creek of cold Clear water. here I tasted the water of the great Columbia river.” He and the other members of the Corps of Discovery had just crossed the east-west continental divide at Lemhi Pass on today’s border between Montana and Idaho. Shortly before crossing, Lewis had straddled a rivulet trickling from a spring on the east side of the line that slipped downhill to join other streams heading east and south for the Missouri River and the Gulf of Mexico. Two additional divides frame the vast interior basin of the Missouri-Mississippi river system. The first lies to the north at Browns Valley, a town on the Minnesota– South Dakota line, where water from the Red River, which rises in Minnesota, turns north toward Canada. The second lies to the east, along the north-south crest of the Appalachian Mountains, between the Atlantic coast and the rivers of the interior. The Pacific, Gulf of Mexico, and Hudson Bay watersheds meet at the summit of Triple Divide Peak in Glacier National Park. To the west the peak drains into the Flathead River, thence to the Pacific via the Columbia River. To the northeast it flows into the Saskatchewan River and on to Hudson Bay. On the southeast its waters enter the Marias River and flow on to the Gulf via the Missouri and Mississippi. In “Once by the Pacific,” Robert Frost writes: “You could not tell, and yet it looked as if/The shore was lucky in being backed by cliff/The cliff in being backed by continent.”

Conger Beasley, Jr.