I don't think the Northern Ontario/Northern Manitoba is viable as a single state before the era of air travel simply because it's too geographically huge. There are no rivers that run east-west between the two, and the land is Canadian Shield, so horrible for building railroad or road on. Especially if you have the capital near lake Superior or Huron (where most of the population is), you have no reasonable transportation route from there to Northern Manitoba that doesn't go through Southern Manitoba.... The best option would be rail to one of the rivers that drains into Hudson Bay, boat through Hudson Bay to the mouth of one of the other rivers...
So, while it has enough population to be viable, I really thing that Northern Manitoba is more reasonably lumped in with Southern Manitoba or with Northern Alberta/Saskatchewan, which can both be reached fairly easily from Northern Manitoba by river.
I think the most viable option for the "prairie states" is to draw a line just south of Edmonton, and to make everything north of there a single state with Edmonton as the capital. You have enough East-West rivers to connect the region, and you have enough population around Edmonton to serve as a capital. Then, do whatever you want with the Southern Prairies.
A couple other thoughts:
(a) If OTL's Western Canada joins the US before the mid-19th century, I don't think you'd get the straight line along the 49th parallel that you've drawn. I think instead you'd see states the straddle the OTL border, like you've done with the Northern BC/Southern Alaska State
(b) I think Vancouver Island should be a separate State as it was a separate province for a bit OTL, and dividing Vancouver Island from the mainland makes more sense population-wise then cutting up BC North/South. Or even dividing BC between Coast/Interior along the peaks of the Coast Range.
(c) If you are going to divide BC North/South, then the dividing line should be another few hundred km south to make sure that Prince Rupert (Northern BC's principal port) and Prince George (Northern BC's largest city) end up in the Northern half.