On I-90 westbound just short of Vantage, Washington, there's an exit that leads to a parking lot and a "WATCH FOR RATTLESNAKES" sign. The terrain's typical for that area of central Washington state, a lot of raw rock speckled with hardy plants that look like they're waiting for a cowboy to come riding past in a cloud of dust. The wind is cool while the air is warm - at least it was when I was there - and the chitters of distant critters and the rumbling of the vehicles passing by on the nearby freeway are swallowed in the open vastness.
Also, the Columbia River is there. It's huge - one of the largest rivers west of the Rockies, and of those I've seen in person, only the St. Lawrence and Mississippi compare. This river was sought after by explorers for decades, and was one of the keys to European settlement of the Pacific Northwest. Significant diplomatic conflict between the United Kingdom and an expansionist United States pivoted around the river and its watershed in the mid-19th century. In the end the border was settled straight along the 49th parallel, and geographical oddities like Point Roberts just had to deal.
Still, while passing through Seattle, I couldn't help but think that it would be great to be able to go there without needing a passport. There are three ways I can think of to go about this. First is, of course, fixing the restrictions: up until a couple of years ago, a driver's licence or birth certificate was more than enough for a Canadian to wend across the border, no huhu. The second, a bit less practical, is to dust off the owner's manual for your time machine and hop back to 1992 for some score swingin' on the flippity-flop. The third is mostly academic, but is interesting in its own right - go back and manipulate history so that Seattle, or at least the ground on which it's built, was always part of Canada.
This is something I thought about on the way back to Vancouver, and particularly in the forty-minute lineup to clear Customs at Surrey.
I'm not going to be indulging in a fully-realized alternate history here - those are of wizard complexity considering the degree of factors which must be taken into account; could be a job well-suited for a sapient computer, perhaps. The biggest bugbear - how - isn't one I'm going to get into, though it's not because I'm short of possibilities. Perhaps the American government becomes willing to grant concessions in the Pacific Northwest from British arm-twisting of the Mexicans in California; perhaps Captain Vancouver recognizes the Columbia River for what it is on that day in 1792, in which case the United States loses the "finder's keepers" argument and the river ends up with some other name entirely. Could be that something really unlikely happens too.
Sure, I know it's not exactly the likeliest possibility - the United States in the nineteenth century was rather hungry for territory, and didn't part with it lightly - there are absolutely aspects of our own history that are low-probability; perhaps smart folk back when would've put their money on the Confederation of North America and not the United States of America. Ultimately that part of Washington state north and west of the Columbia could easily be folded into Canada, or whatever unified British North America calls itself; Portland becomes a border town and Spokane might end up part of Idaho.
The question I tossed around was this - how does the development play out? Will alternate Vancouver - which I'll mark with an asterisk - become Canada's Pacific metropolis, or would *Seattle? Or both? I did some looking into this, and came up with the "Seattle, British Columbia" thread by David Tenner on soc.history.what-if, which looked into this same issue back in 2007. It's not surprising; there's scarcely a mote of potential alternate history that SHWI hasn't chewed on over the last fifteen years. But the discussion within did wake me up to a factor I hadn't considered.
I already knew that the railway was important. Vancouver is what it is because it's the western terminus of the Canadian Pacific Railway; had the original plans come to fruition, the tracks would have stopped in New Westminster and the developmental patterns in Metro Vancouver would've been considerably different. I hadn't thought about the issue of the mountain passes, though - and from what I've read, the Canadian railway planners weren't exactly spoiled for choice, as the really ideal mountain passes seem to require running rails through what would be American territory even with Canada on the Columbia. From my admittedly limited comprehension of the issue, it seems plausible that *Vancouver - or *New Westminster, for that matter - would be the western terminus and the center of development.
That doesn't mean it'd all work the same way, though. Look at a terrain map of Metro Vancouver on Google Maps - there's a triangle of territory from Vancouver to Chilliwack and Bellingham, Washington that's relatively open land surrounded by mountains, restricted only by a line on a map. The lack of a national border would spur *Vancouver's development even further, by removing the only major artificial barrier to development. Possibly the situation would result in something along the Golden Horseshoe model, with *Vancouver and *Seattle the anchors on either side of a more-or-less continuous urban zone. Think of *Surrey as a western reflection of Mississauga, and *Seattle occupying roughly the same position as Hamilton does in Ontario's Golden Horseshoe.
Might be an interesting place to set a story, once the holes in the theory - and I'm sure there are many - could be identified and filled in. Would have to come up with names, though. At the least I have reasons to doubt that "Seattle" would come up in the alternate - which is unfortunate, since it's a good name.