What is the longest river in the United States?

Factual Questions
1

I had assumed this would be a simple question, but from doing a fair amount of research on the Internet, it seems like this is an issue that there is not a lot of agreement on.

The reason I started looking into this is because a friend of mine was doing a quiz online, and they were told that answering Mississippi as the longest river in the US was incorrect. They looked it up in the World Book (only reference material they had at the time I guess) and the World Book says:

“The Mississippi River is the chief river of North American and is the longest river in the U.S.  It flows 2,348 miles from its source in northwestern Minnesota to its mouth in the Gulf of Mexico.”  (Vol. 13, p. 540)"

and

"The Missouri River is the second longest river in the U.S.  Only the Mississippi is longer.  The Missouri flows 2,315 miles from its headwaters in Montana to its mouth on the Mississippi. (Vol. 13, p. 560).

Despite my opinions on the World Book, this seems fairly factual, and I wouldn’t think there would be much confusion.

But after searching the Internet, I have come up with both references that support this claim (Mississippi is longest river, Missouri is the second longest) and others that are the exact opposite.

For example, there is a site called http://www.longestriver.org which claims the Missouri is the longest, but doesn’t give any numbers.

I then found a site run by the Discovery Channel, at http://school.discovery.com/homeworkhelp/worldbook/atozgeography/m/364860.html which says

“Missouri River is the longest river in the United States. It flows 2,540 miles (4,090 kilometers) from its source, the Jefferson River at Red Rock Creek in southwestern Montana, to its mouth on the Mississippi River.”

So my first question is how one place could say the Missouri is 2540 miles, and another would say it is 2315 miles. That is a pretty big difference, and you think in this day and age people could agree on something like the length of a river.

I also found another site at http://explorezone.com/archives/00_04/03_drought.htm they say:

"The Mississippi River, in particular, is crucial to the health of the nation’s waterways. As the longest U.S. river at 2,340 miles (3,765 kilometers), it drains 40 percent of the country’s streams and rivers. "

So while they say the Mississippi is longest, they also say it is 2340 miles, whereas the World Book said 2348. Why even an 8 mile difference?

This site, http://www.amrivers.org/missouririver/moabout.htm also says the Missouri is the longest River and quote a 2500 mile figure, and they would seem to be more reliable since this whole orgnization and site is about American Rivers.

Any help on this would be much appreciated. I’m just personally curious about this issue, why there is so much difference in the numbers, and why there seems to be such disagreement on the longest river. It seems like this should be fairly straightforward.

Or is this another one of those issues like “what is the world’s tallest building” that depends on exactly what people decide is the river and what isn’t?

Thanks!

2

In a recent geography book I read, it said that the longest river is the Missouri-Mississippi. I believe it went on to add that the Mississippi from St. Louis down was mis-named and should be called the Missouri. This is because the Missouri is the larger river, and the Mississippi is the tributary.

3

I was wondering why you hadn’t posted this in Great Debates? :wink:

Your last statement sums up the situation quite accurately.

We went through a discussion on the subject almost two years ago that lays out most of the measuring points and includes several of the discussions points of “how” to measure rivers. The Mississippi or Missouri Read it quick. It was last touched in 1999 and is open to purging at the moment.

4

I did a search on the Straight Dope archives, but didn’t think to search the messageboards…thanks for pointing that thread out.

It seems like with this much debate some of these places (especially the Discovery Channel and that American Rivers site) would at least include a mention that there is a debate about the actual length of these rivers, instead of just factually stating one way or the other the lengths of them.

5

What! And not be perceived as the Oracles of Truth?

6

I started a thread on this subject some time back, but I’ll wait until later to search for it.

If you start at the mouth of the Mississippi and move upstream, you will have to decide which stream is the main river when two tributaries come together. Logically, the stream you follow is the one with the larger flow. In that case, you would follow neither the Upper Mississippi nor the Missouri, but the Ohio. Beyond Pittsburgh, you’d follow the Allegheny.

On the other hand, if you’re looking at a map, you might choose the stream along which water has flowed the greatest distance. In that case you’d follow the Mississippi-Missouri-Jefferson-Beaverhead-Red Rock to it’s most distant source, Upper Red Rock Lake in SW Montana. That seems kind of convoluted, but when you’re trying for third place among long rivers worldwide, you’ve got to stretch things as far as you can.

The Mississippi wasn’t named by either of those two methods. It was named by French explorers travelling downstream from Minnesota, where the stream was called the Mississippi by the local Indians.

7

Yet another technique I might use would be that if one branch isn’t clearly bigger, the one that forms less of an angle at the junction is the main river. Sort of like I expect street names to behave.

8

Good point, yabob. It looks like the Ohio would beat out the Upper Mississippi by that criterion, but the Upper Mississippi would beat out the Missouri.

Another criterion I thought of is the size of the drainage basin. In that, the Ohio and Upper Mississippi both lose out to the Missouri. I’m pretty sure the Ohio basin is bigger than the Upper Mississippi basin, though.

I tried searching for the thread I mentioned above, but I couldn’t find it. Perhaps I never actually posted it.