It's an interesting concept. I'm not sure I agree with sticking the capitol out in the middle of nowhere. I would be more inclined to make Vancouver the capitol, as it would be the largest city in Cascadia, and have the amenities to make it suitable as a capitol city: i.e. a large port, large airport, good accessible location, and most of all - already developed. Seattle would still be a very large and important second city.
It would appear that the capital city of Cascadia is Smithers, BC. That will change quickly.
Smithers is, just possibly, the most beautiful small city in "the best place on earth", which would make it the best small city on earth. As fine a place as any to be the capital city of an imaginary republic.
BTW, shouldn't Alaska be part of this? I think so...
Before anyone gets too involved in an earnest discussion of a very silly idea, we should keep in mind that the creator of the Republic of Cascadia website is a spoof artist. Another one of his ideas is 'tree octopuses'.
With all the economic and political turmoil in the world today, I'd say anything is possible. It's already been pointed out that this is an old idea, so even if this particular website is a spoof, I think there has been some more serious consideration - maybe not so much as a separate country, but as an economic region. And I think this idea has influenced political and economic cooperation within the region in recent decades.
It might as well include Alaska and the Yukon.. and Idaho.
And who wouldn't want Alberta? Haha.
Seriously, it does have some historical basis, weak as it is. During the fur trading days, the Columbia District or 'Oregon Country' encompased most of BC, Washington, and Oregon - before the British and Americans divided it up. Back then California was part of Mexico I believe. Perhaps you could make this historical argument even further back, with the First Nations of the "Pacific Northwest" having some common links.