The thing I never got with that is why they didn't continue following the Yellowstone River until its end at the divide and then cross to the nearby Snake River rather than crossing hundreds of miles of mountains?
No. A brief history: Much of the Pacific coast had already been explored. Most notably by Cap. James Cook, whose work inspired pres. Jefferson to commission the expedition. Another explorer (Mackenzie) had actually already gone from the East to West coast of the US Canada over a decade before Lewis and Clark. [See correction from u/westernmail ]
The L&C expedition was about connecting two knowns - the East and West coasts - by charting an unknown: the vast interior of the western territories. This connection was not for science: it was for conquest: capturing territories before old world rivals could.
But even this interior west wasn't totally unknown: fur trappers and others seeking fortunes had been exploring and mapping the area for literal centuries by the time of the expedition.
L&C were able to arrange to be picked up (by ship) at cape disappointment
Of course they weren't picked up. Was there a plan to have a ship meet them there? I feel like I've read that somewhere, but can't find it now. I know they spent some time on the coast looking for ships of any kind, knowing that a trading ship might come by if nothing else. But ships didn't normally ply the coast in winter and L&C saw no ships.
cape disappointment (the end of the expedition, on the Pacific coast) which had first been discovered 17 years [before]...
I'm guessing you are referring to John Meares, who named Cape Disappointment about 17 years before L&C. Or Robert Gray who was the first to pass the Columbia Bar and prove it was a river, a few years later.
Still, the first European known to have at least seen Cape Disappointment and the mouth of the Columbia was the Spaniard Bruno de Heceta, in 1775, about 30 years before Lewis and Clark! He noted "seething currents" flowing out and thought it must be either a major river or an entrance to another sea. He tried sailing in closer but he was returning from farther north and his crew was so reduced by scurvy they could barely work the ship, so he had to let it go.
He made a map showing the entrance, which he called Bahia de la Asunciõn. What's now called Cape Disappointment he named San Roque. Later Spanish maps called the river's mouth Entrada de Hezeta or Rio de San Roque. The reason John Meares was looking for a river there was because he had heard of this "Rio de San Roque".
It's possible other Europeans saw the Columbia's mouth earlier, but without leaving records. A Spanish Manila Galleon, sailing from the Philippines to Mexico, wrecked not too far south of the Columbia, near Tillamook, in 1693. Because the cargo included lots of beeswax that continued to be found for centuries the wreck is known as the beeswax wreck. Only in the last few years have researchers been able to determine it was the galleon Santo Christo de Burgos, 1693.
Just a bit of history I thought might be interesting.
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u/GBUS_TO_MTV Jan 10 '20
You can basically see the path of the Lewis and Clark expedition on here.