Why is the Missouri considered a tributary to the Mississippi?

Factual Questions
21

The Mississippi River drains 1,237,700 square miles and flows 2,348 miles to the Gulf of Mexico.

The Missouri River drains 580,000 sq. mi. and flows 2,714 miles to the Mississippi River just north of Saint Louis.

If the Missouri were to be considered to be part of the Mississippi, then the total length would be 3,892 miles. Before being dammed in the 1900s, the Missouri flow ranged from a low of 13,000 cubic feet per second during a drought to 800,000 cfs in a flood and it transported about 550,000,000 tons of sediment to the Mississippi River every year. .

The Mississippi was explored and exploited in 1673 by, as stated earlier, by Louis Joliet and Father Jacques Marquette, the former to expand the territory for the lucrative fur trade and the latter to save more souls. They reached the north end on June 17, 1673, and traveled south, passing the Missouri, which they named after a nearby tibe of Indigians. Fearing capture by the Spanish if they went further South, they stopped at the Arkansas River.

The upper reaches of the Missouri were reached only in 1739 by Sieur de la Verendrye.

Joliet and Marquette were not the first Europeans to find the Mississippi, as Hernando De Soto “discovered” it in April 1541, having pillaged and burned the Southeast all the way from Florida for two years, looking for gold.He died on May 21, 1542, and his second-in-command, Luis Moscoso, disposed of his body in the Mississippi so as to not let the Indigians know of his passing. Moscoso then led the remainder of the expedition to the Gulf of Mexico. Only 311 of the more than 600 original survived. Further exploration of the river would not happen for nearly 100 years. (DeSoto’s descendants can now be found in the Hilton Hotel in Savannah, Ga., and running around Havana, Cuba. Just kidding.)

(cite: Bartlett, Richard, A., Editor, Rolling Rivers-An Encyclopedia of America’s Rivers, McGraw-Hill, NY, etc., 1984, pp. 206-213)(not verbatim)

22

Ignatz, the drainage basin figure you quote for the Mississippi includes all the basins of the “tributary” rivers, such as the Arkansas, the Ohio, etc. If you limited the drainage basins to what was drained up to the point of the junction, I think you’d find that the Missouri is both longer and bigger than the Mississippi. However, the average flow rate for the Mississippi is slightly higher at that spot.

Curiously, if the Ohio River were to have entered the Mississippi ABOVE the Missouri, there would be no question that the Ohio would be the main river all the way down. Its flow rate at the junction with the Mississippi is only less than the Mississippi because of the contribution of the Missouri River just a few miles upstream.

23

Yes, Ignatz, check out this cute watershed map. DSYoungEsq is right; the drainage basin I’m talking about is the Upper Mississippi in that link. If the naming convention had been used, the river should have been called the Missouri all the way to the Gulf. See what I mean?

DSYoung: I dunno about the Ohio. The drainage area is smaller than that of the Missouri.

24

But if the Ohio joined above the Missouri, then the drainage basin would be the Ohio plus the Mississippi. Is THAT smaller? <wonders>

ETA: Remember, add the Tennessee in; it drains into the Ohio.

25

Ah, ok. The handy-dandy little map shows the Tennessee as if it were a tributary of the Miss.

It’s only a matter of addition, but I have not had luck pinning down some of these basin areas. Wikipedia has:

Missouri = 529,350 sq. mi.
Upper Mississippi = 3,296 sq. mi.
Ohio (including Tn?) = 189,422 sq. mi

The articles are not clear about what is included/excluded from those basin numbers, so take them with a grain of salt.

A little off topic, have you read about the Teays river, an historic predecessor of the Ohio? Interesting stuff.

26

That number is very wrong, if only because the Missouri is technically a tributary of the Upper Mississippi. But even disregarding that, the river is >1000 miles long, so to get a drainage basin that small would require that it extend no more than a mile and a half to either side of the river throughout its course. This site gives a more reasonable figure of 189,000 sq. mi. for the Upper Mississippi’s basin (and does not appear to include the Missouri’s drainage basin).

27

The Library of Congress web site is a good site to look for old maps too.

28

Good site, MilTan. :slight_smile:

Still, using that figure, and the figure for the Ohio River, it would appear that the Missouri drains an area not quite half-again as big as the Upper Mississippi + Ohio.

Since the flow rates clearly are much larger for the Upper Mississippi + Ohio compared to the Missouri, it would be interesting to see what current thought on the naming convention would be…

29

And this was before tampons.

30

"

According to Wikipedia this is correct in normal times, but not by a whole lot. And if the Upper Midwest is having a relatively dry year the volume of the Missouri at the confluence may be more than that of the Mississippi. It certainly isn’t a case of a much smaller river joining a large one, but more like a merger of equals.

Still, the Mississippi was known and explored first, so it was natural for cartographers and geographers to discuss and map it as the main important river.

31

So, if the situation were fixed, and the Missouri (or the Ohio) were considered the main river, entering the Gulf of Mexico after being joined by the Mississippi and the Ohio, not to mention all the other major rivers that join this group; would the world statistics on river length be modified? Are there other ‘record’ rivers than pose this issue?

32

"Well, you can see roughly how it looked in Lewis and Clark’s day on the map here - different, yes, but the Missouri still came in from a near 90-degree angle. "

I think the hard turn is more due to the geologic influences of the Ozark Dome and the extent of the glaciers. If you look at a map you can see the Mississippi also makes a hard left running parallel with the Missouri just before combining. The Missouri River makes a couple of hard turns at Kansas City and again near Booneville, MO. I think these are a result geologic and glacial influences.

Perhaps the more appropriate naming should have been the Louisiana River from the Gulf to Montana. Since it does drain most of the Louisiana Purchase. Although the purchase post dated the naming.

As far as primary river, I think the biggest drainage basin is always primary because it has the potential to be the biggest. Its just a matter of average precipitation. If a climate shift made the great plains get as much rain as the Ohio River basin, there would be no comparison on size, but the Missouri basin is pretty dry. The river gains a large portion of its average flow in the state of Missouri, the Osage River joins the Missouri River in central Missouri and is said to provide a 7th of the average flow and it is only 500 miles long and it starts in eastern Kansas.