Knowing what we know now, of course… Two things to keep in mind: They were charged with finding the headwaters of the Missouri River (determining the extent of the nation’s purchase) and finding an easier (all or at least mostly water) passage to the Pacific Ocean.
My thoughts on living in the PNW all my life would be that they should have / should have headed south over Monida Pass (rather than Lemhi Pass to the Clearwater River) and then followed the Snake River to the Columbia and yadda yadda. Granted, Hells Canyon would have been no picnic but having rafted it, I can attest that they could have portaged around the more difficult rapids as they usually did.
Mods, feel free to move this IMHO is there is no objective, opinionated answer to this question.
I believe the Snake River in Hells Canyon was quite a lot more treacherous before the hydroelectric projects
While we’re being armchair explorers, what they really should have done is after considering for a week at the confluence of the Missouri and Marias River, they should have taken the Marias River instead. Marias Pass is the easiest pass over the continental divide in the Northern Rockies. Only a relatively short portage over a wide relatively gentle pass separate the Marias from the Flathead river, which flows into the Clark Fork and then into the Columbia without any major obstacles. This actually could have been a major counter-factual turn of events in US history in general because as it was Marias Pass was only charted in 1889, but had it been discovered by L&C it could very well have become the primary migration route to Oregon and the rest of the northwest.
1806: Lewis and Clark
what does the exact date of discovery matter ?
What was significant about the discovery, that isn’t expected,known…
( They knew about rivers, rocks, forests, ocean… )
Whom are the actors for which it would matter ?
French, British (Canada) ? Nope. too far away, they didn’t even get Alaska
Russians. Nope. Nowhere near
Spain ? perhaps
Mexico ? perhaps
1848: California Gold Rush
So if Lewis and Clark had gone further south, they might have found gold,
and an earlier gold rush could have induced a larger population of Spaniards or Mexicans… And then California through to Texas might not have become USA territory.
Yet, Hells Canyon could be avoided (again, knowing what we know now) by heading overland via what is now La Grande, now Interstate 84. It’s just that I’ve been over many of these passes and Monida always stuck me as the most gradual, gentle pass I’ve ever been across. More of a high spot in the road than anything. The only sign that you’ve reached the top of the pass is literally a sign on the road noting the elevation.
Clark Fork is really the only other alternative and in fact, I will be canoeing a portion of it next month. Clark Fork to Pend Oreille and eventually the Columbia. Of course, the Pend Oreille River flows so far north that Lewis & Clark might have been concerned that they weren’t even in the Columbia River watershed.
Part of the reason they wound up taking the path they did was to keep close to the same latitude as the mouth of the Columbia. But my rules as set out in the OP is knowing what we know now. I’m rereading Undaunted Courage for the third time which is what prompted these thoughts. I’m far from a Lewis & Clark buff but what an amazing true-life adventure story. How my high school history teacher managed to make it boring always amazed me.
If they didn’t care for the looks of Hells Canyon (on the Snake River BTW, not the Salmon as the wiki author writes) they would have hated the Salmon River itself. After crossing Lemhi pass the locals dissuaded them from attempting to descend the Salmon describing it as nothing but whitewater and sheer rock canyons. I’ve rafted the Middle Fork and we tore out the bottom of our raft on the first day and there was literally no place to beach to make repairs for many miles. It was a rather unpleasant experience.
Seems to me a really good route would have been to follow the Madison rather than the Jefferson River out of Three Forks MT. From the point where the Madison River emerges into its major valley, it’s an easy 12-mile walk south, across a notably low (6830’) point in the continental divide, to Henrys Lake, source of the Henrys Fork of the Snake River.
So you have a route with no severe mountains to cross and only a very short distance not covered by raft-navigable rivers.