# How did Jefferson know that the sources of the Missouri and the Columbia Rivers were near eachother? **URL:** \ **Category:** Factual Questions\ **Created:** [October 27, 2015, 2:30am UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839 "2015-10-27T02:30:09Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [October 27, 2015, 7:08pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/21 "2015-10-27T19:08:54Z")
I’d have taken the I-80 to Salt Lake and then up the I-84 to Portland, that’s the easiest way with oxen-teams. ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [October 27, 2015, 7:18pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/22 "2015-10-27T19:18:55Z")
> [@Freddy\_the\_Pig](#): > > And in fact this turned out to be a poor algorithm for finding the best land route across the Continental Divide. The easiest land route, as it turned out, was to break off from the Missouri early and follow the North Platte to the table-land of southern Wyoming, cross the Divide, pick up the Snake River valley, and then cut across to the Columbia. This was the route used by the Oregon Trail. > > The Lewis and Clark route, by contrast, was completely impractical and few later parties attempted it before the automobile. Even today, it runs through some of the least populated parts of the United States. As Ian Frazier has remarked, Lewis and Clark were not so much the forerunners of a new civilization as the forerunners of future Lewis and Clark buffs. One of the big counter-factuals of the expedition is that at the mouth of the Marias River, they initially thought the Marias was the main channel of the Missouri. After spending several days agonizing over it, they eventually did correctly pick the main channel, past the Great Falls and eventually on into getting lost in the Idaho high country. If they’d followed the Marias like they originally thought, they would have discovered Marias Pass which not only would have got them to the Columbia _much_ faster, but the Marias route could very well have become an alternative to the Oregon Trail. Marias Pass is the lowest and gentlest of passes across the Northern Rockies (it’s the main rail route today) but it was only discovered in the late 1880’s. ---
**Author:** ![JKellyMap](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jkellymap/32/15880_2.png) [@JKellyMap](https://boards.straightdope.com/u/JKellyMap)\ **Post date:** [October 27, 2015, 8:10pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/23 "2015-10-27T20:10:09Z")
> [@Chronos](#): > > And not even always that, as evidenced by the Mississippi, which has at least one and possibly two (depending on how you define size) “tributaries” larger than it. I was going to mention that! For the benefit of others: we’re pointing out that the Missouri River is bigger (main channel longer, more volume at mouth, larger watershed…) than the Mississippi-north-of-St.-Louis River, and even the Ohio River is by some measures bigger than the Mississippi-north-of-Cairo River…so the Missouri should be called the Mississippi, and the Mississippi-north-of-St.-Louis should be called something else. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [October 28, 2015, 12:29am UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/24 "2015-10-28T00:29:38Z")
And the part below Cairo should be called the Ohio". ---
**Author:** ![glowacks](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/glowacks/32/5548_2.png) [@glowacks](https://boards.straightdope.com/u/glowacks)\ **Post date:** [October 28, 2015, 1:52am UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/25 "2015-10-28T01:52:33Z")
[![](http://mississippivalleytraveler.com/wp-content/uploads/Flow-data-in-tabular-form_Page_1.jpg) ](http://mississippivalleytraveler.com/wp-content/uploads/Flow-data-in-tabular-form_Page_1.jpg) Flow rate clearly more than doubles when the Ohio enters, suggesting that the Ohio be considered by at least one measure the main channel. ---
**Author:** ![chacoguy](https://avatars.discourse-cdn.com/v4/letter/c/50afbb/32.png) [@chacoguy](https://boards.straightdope.com/u/chacoguy)\ **Post date:** [October 28, 2015, 3:06am UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/26 "2015-10-28T03:06:15Z")
> [@chappachula](#): > > Yeah, you deserve to feel embarrassed—for posting a link to a one-and-a-half-hour long video, with no explanation. > > Do you expect me to watch all of it, just because you posted it? > How ‘bout, ya know, tellin’ us a little bit about the content? Maybe even suggest jumping to a specific part of the clip that’s relevant? Sorry about that, I thought that I had linked to around the seven minute mark. So, the answer to my own question; Jefferson, Lewis and Clarke had no idea what was out there. That was the point of the expedition. They would have learned a great deal even if they proved that trans continental travel was impossible. Then, by extraordinary luck, they met Sacajawea who guided them across the plains. The against lottery odds, she found her brother living at the base of the passes they needed to cross. So, it was blind groping and extraordinary luck. ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [October 28, 2015, 5:04am UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/27 "2015-10-28T05:04:53Z")
> [@Freddy\_the\_Pig](#): > > Lewis, Clark, and Jefferson were all _disappointed_ that there was no easy portage between the Missouri and Columbia watersheds. Jefferson rather naively thought that it would be like going from the Great Lakes to the Mississippi–just carry your canoes for a few miles across what is now Chicago, and you’re good to go. That obviously wasn’t the case. The Rockies are a bit more formidable than Chicago–maybe not in baseball, but in geography. Why did they think that? Mackenzie’s two expeditions (to the Arctic, 1789) and to the Pacific Ocean (1792-93) clearly demonstrated the size of the continent, and the mountainous nature of the west coast. Mackenzie published his journals in 1801, three years before Lewis & Clark set out, so you would think Jefferson and L&C would have had some inkling of the task they faced. ---
**Author:** ![Freddy\_the\_Pig](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@Freddy\_the\_Pig](https://boards.straightdope.com/u/Freddy_the_Pig)\ **Post date:** [October 28, 2015, 1:56pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/28 "2015-10-28T13:56:07Z")
> [@Northern\_Piper](#): > > Why did they think that? Mackenzie’s two expeditions (to the Arctic, 1789) and to the Pacific Ocean (1792-93) clearly demonstrated the size of the continent, and the mountainous nature of the west coast. > > Mackenzie published his journals in 1801, three years before Lewis & Clark set out, so you would think Jefferson and L&C would have had some inkling of the task they faced. Yes, all of that is true. Jefferson’s notion that “a single day’s portage” might connect the Atlantic and Pacific watersheds was frankly ridiculous by 1803. It was a case of wishful thinking, backed by legends and mis-translated bits of Indian lore, overriding hard fact. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [October 28, 2015, 2:20pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/29 "2015-10-28T14:20:12Z")
Which hard facts, we didn’t know where the Missouri source was nor the Columbia source, the lands in between were pretty much _hic sunt dracones_ as far as Jefferson knew. HBC may well have known differently, but do you honestly think George III would help the USA claim the Oregon Territory in 1803? Perfectly natural thing to do, once we doubled the size of our nation, we went and explored it. ---
**Author:** ![Freddy\_the\_Pig](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@Freddy\_the\_Pig](https://boards.straightdope.com/u/Freddy_the_Pig)\ **Post date:** [October 28, 2015, 2:31pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/30 "2015-10-28T14:31:17Z")
> [@watchwolf49](#): > > Which hard facts, we didn’t know where the Missouri source was nor the Columbia source, the lands in between were pretty much _hic sunt dracones_ as far as Jefferson knew. Only because he rejected anything that fit his preconceived notions. Nobody knew _exactly_ where the sources of the Missouri and Columbia were, but it should have been clear to anyone reading Mackenzie or the reports of British _and American_ captains who had explored the Pacific coast that it was a very mountainous area and the river sources were all but certain to be separated by weeks of hard travel. > [@watchwolf49](#): > > Perfectly natural thing to do, once we doubled the size of our nation, we went and explored it. Of course. But Jefferson should have been more realistic about what to expect. To the credit of Lewis and Clark, the unrealistic expectations did not impede their progress. They improvised well and traveled as well by horseback as by keelboat. But still, the expectations were unrealistic. ---
**Author:** ![Northern\_Piper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/northern_piper/32/5304_2.png) [@Northern\_Piper](https://boards.straightdope.com/u/Northern_Piper)\ **Post date:** [October 28, 2015, 3:07pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/31 "2015-10-28T15:07:08Z")
> [@watchwolf49](#): > > HBC may well have known differently, but do you honestly think George III would help the USA claim the Oregon Territory in 1803? Mackenzie was North-West Company, not HBC. In any event, George III had nothing to do with it. There had been British, American and Spanish naval explorers up the Pacific coast in the 1790’s, as well as Mackenzie’s two overland expeditions. Mackenzie and Vancouver both _published_ accounts of their travels, which came out some years before Lewis & Clark set out. If Jefferson did in fact have the world’s largest collection of books on North American geography, as posted upthread, then he should have had those two sets of accounts, which clearly established the longitudes of the western coast of North America and its mountainous nature. ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [October 28, 2015, 5:18pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/32 "2015-10-28T17:18:38Z")
> [@Freddy\_the\_Pig](#): > > Yes, all of that is true. Jefferson’s notion that “a single day’s portage” might connect the Atlantic and Pacific watersheds was frankly ridiculous by 1803. It was a case of wishful thinking, backed by legends and mis-translated bits of Indian lore, overriding hard fact. Well, except for the fact that the easy portage _does_ exist in a few places. L&C just didn’t find any of them. Unlike the Canadian Rockies, the US Rockies aren’t just a continuous chain of mountains. There’s lots of easy ways across. In 1803 before they set out, they might have known McKenzie had encountered a seemingly unbroken chain of mountains to the north, but Spanish explorers like Coronado and Kino had found arid but easily skirtable mountains to the south. Expecting something like the middle of those two extremes wouldn’t have been unreasonable and is in fact more or less what exists. On the “Indian lore” front, there was plenty of trade between the Pacific coast and inland NW, and trade between the inland NW and the Great Plains. So certainly at least by the time L&C wintered at Mandan Villages, they would have had some vague confirmation that passable routes existed very far west into the mountains if not all the way to the coast. ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [October 28, 2015, 6:14pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/33 "2015-10-28T18:14:25Z")
> [@Freddy\_the\_Pig](#): > > Jefferson’s notion that “a single day’s portage” might connect the Atlantic and Pacific watersheds was frankly ridiculous by 1803. As GreasyJack notes, it’s not ridiculous today. Consider the route from the Madison River to the Henry’s Fork of the Snake River: about 13 miles, rising gently ~700’ to a maximum altitude of around 6800’, then descending gently to around 6400’. (To be sure, some sections of the Snake River Gorge a couple hundred miles downstream would have been no picnic.) ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [October 28, 2015, 6:21pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/34 "2015-10-28T18:21:13Z")
> [@chacoguy](#): > > … they met Sacajawea who guided them across the plains. This is a bit strange - it was the Missouri River that guided them across the plains. ---
**Author:** ![Dallas\_Jones](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dallas_jones/32/3277_2.png) [@Dallas\_Jones](https://boards.straightdope.com/u/Dallas_Jones)\ **Post date:** [October 28, 2015, 7:27pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/35 "2015-10-28T19:27:17Z")
> [@chacoguy](#): > > Then, by extraordinary luck, they met Sacajawea who guided them across the plains. The against lottery odds, she found her brother living at the base of the passes they needed to cross. > > So, it was blind groping and extraordinary luck. Sacagawea was brought along as more of interpreter than guide. She didn’t have any choice. While freezing their asses at Ft. Mandan that winter, Lewis and Clark met her husband Charbonneau and learned that she could speak Shoshone, which was the language that they expected to meet somewhere in the Montana/Idaho area, before those places were named. And they needed horses, which they expected to get from the Shoshone. She was stolen or taken as a slave from that area when much younger. Her contributions to the Corp of Discovery are amazing! But to keep perspective, she started the trip as just the 15 year old pregnant wife of a Quebecois trapper. She was captured as a slave before she married the trapper, much younger and getting married at 13. Or more likely just bought. So her knowledge of the land and passes would be rather limited. But still, Lewis thought he might need them so he took them along. Smart move. Still, it is just a wonder that these people managed to cross the continent, a lot of it on foot, and they did not get killed a couple of times each. They all walked, canoed, drifted when possible, and rode a few horses all they way. And back again! Amazing. If records are ever lost, this story will get passed down like a work of Homer, whoever he was. A timeless myth. ---
**Author:** ![Common\_Tater](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/common_tater/32/13846_2.png) [@Common\_Tater](https://boards.straightdope.com/u/Common_Tater)\ **Post date:** [October 28, 2015, 10:25pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/36 "2015-10-28T22:25:14Z")
They did run out of booze and smokes, but it’s said that upon their return they had enough ammunition - powder and lead - to repeat the entire expedition if necessary. Somebody hit upon an ingenious method of making the powder containers out of lead in the amount proportionate for a standard load, and sealing them as to be waterproof. There were some caches left around Great Falls and researchers have some hope yet of maybe finding some artifacts. Maybe ground penetrating radar will help in this regard. Known artifacts from the expedition are quite rare. ---
**Author:** ![chacoguy](https://avatars.discourse-cdn.com/v4/letter/c/50afbb/32.png) [@chacoguy](https://boards.straightdope.com/u/chacoguy)\ **Post date:** [October 28, 2015, 11:32pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/37 "2015-10-28T23:32:36Z")
[This museum](http://www.furtrade.org/) has one of the peace Medals. ---
**Author:** ![Freddy\_the\_Pig](https://avatars.discourse-cdn.com/v4/letter/f/a587f6/32.png) [@Freddy\_the\_Pig](https://boards.straightdope.com/u/Freddy_the_Pig)\ **Post date:** [October 29, 2015, 5:44am UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/38 "2015-10-29T05:44:26Z")
> [@Xema](#): > > As GreasyJack notes, it’s not ridiculous today. Consider the route from the Madison River to the Henry’s Fork of the Snake River: about 13 miles, rising gently ~700’ to a maximum altitude of around 6800’, then descending gently to around 6400’. It isn’t enough to identify blue lines on the map that are X distance apart. The rivers have to be _navigable_. The Shoshone Indians specifically warned Lewis and Clark that the Snake was not navigable above its junction with the Clearwater on what is now the Idaho/Washington border, as it was loaded with rapids, canyons, waterfalls, and submerged rocks. Lewis and Clark had already stretched the definition of navigability beyond recognition in ascending the Missouri and Jefferson Rivers. It took them one month–_one month!_–to portage around the Great Falls of the upper Missouri. Further upstream, the Jefferson proved even less hospitable. In the words of historian Bernard DeVoto, > [@](#): > > against a will that was charged with three centuries of desire, the water route of commerce to the Columbia River was being proved an unfruitful dream. They knew now what mountain rivers were: too swift, shallow, and narrow for anything but the towrope, full of boulders, choked with gravel, overhung with brush. Furs and Indian goods and China tea would have to be pulled up and down these streams in unwieldy dugouts at a pace that even roaming hunters on the shore exceeded far. > [@GreasyJack](#): > > Well, except for the fact that the easy portage does exist in a few places. L&C just didn’t find any of them. Unlike the Canadian Rockies, the US Rockies aren’t just a continuous chain of mountains. There’s lots of easy ways across. And those would be what, exactly? If they were “easy”, why didn’t any waterborne commerce or travel from east to west ever develop? Contrast with the situation in the Midwest, where an easy portage _really did_ connect the Great Lakes with Hudson Bay drainage. The fur companies ran brigades of voyageurs over the Grand Portage every summer for decades, maintaining a thriving trade between eastern and northern Canada. ---
**Author:** ![SpyOne](https://avatars.discourse-cdn.com/v4/letter/s/82dd89/32.png) [@SpyOne](https://boards.straightdope.com/u/SpyOne)\ **Post date:** [October 29, 2015, 2:35pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/39 "2015-10-29T14:35:06Z")
> [@JKellyMap](#): > > …so the Missouri should be called the Mississippi, and the Mississippi-north-of-St.-Louis should be called something else. That’s what they taught us in elementary school in Connecticut back in the 70s. ---
**Author:** ![GreasyJack](https://avatars.discourse-cdn.com/v4/letter/g/df705f/32.png) [@GreasyJack](https://boards.straightdope.com/u/GreasyJack)\ **Post date:** [October 29, 2015, 3:37pm UTC](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839/40 "2015-10-29T15:37:01Z")
> [@Freddy\_the\_Pig](#): > > It isn’t enough to identify blue lines on the map that are X distance apart. The rivers have to be _navigable_. The Shoshone Indians specifically warned Lewis and Clark that the Snake was not navigable above its junction with the Clearwater on what is now the Idaho/Washington border, as it was loaded with rapids, canyons, waterfalls, and submerged rocks. > > Lewis and Clark had already stretched the definition of navigability beyond recognition in ascending the Missouri and Jefferson Rivers. It took them one month–_one month!_–to portage around the Great Falls of the upper Missouri. Further upstream, the Jefferson proved even less hospitable. In the words of historian Bernard DeVoto,And those would be what, exactly? If they were “easy”, why didn’t any waterborne commerce or travel from east to west ever develop? Contrast with the situation in the Midwest, where an easy portage _really did_ connect the Great Lakes with Hudson Bay drainage. The fur companies ran brigades of voyageurs over the Grand Portage every summer for decades, maintaining a thriving trade between eastern and northern Canada. Well, yeah, obviously most western rivers aren’t really “navigable” in the sense of being viable for barge traffic, but things like the Madison to the Henry Fork wouldn’t have been much worse than what they’d already been through. Another one I’d point to is again Marias Pass. It’s about 30 miles with a very gentle 1,000 ft of elevation from where the Marias River stops being realistically floatable to the Flathead River. From there, the Flathead actually is a pretty good river (by western standards) and it would have been fairly easy for them to follow that to the Clark Fork and Pend Orielle and then the Columbia. More generally, though, my point is that the major impediment to north woods style river travel in the American West was the aridity and lack of major rivers, not the mountains. There’s lots of very easy overland routes through the mountains, just usually no rivers connecting them. Saying Jefferson et al were “delusional” based on MacKenzie’s account isn’t really right because what MacKenzie found in Canada were nigh-impassible mountains but good rivers on both sides. Their geographical speculation that the unbroken chain of mountains didn’t go all the way down to Mexico turned out to be completely correct, they just didn’t really know how arid the interior West would turn out to be. [Previous page](https://boards.straightdope.com/t/how-did-jefferson-know-that-the-sources-of-the-missouri-and-the-columbia-rivers-were-near-eachother/735839.md?page=1)