I think the biggest reason for our population to be concentrated along the border has to do with weather. The further south, the better the weather, in general.
The fairer winter weather is actually on the coasts. There is lots of reasons why metropolitan areas build up where they do. Oroville, Washington (pop. 1,686, income $22,301 per household) and Osoyoos, BC (pop. 5,085, income $43,764 per household) have the same weather, they share the very same lake. But one (Osoyoos) is much more prosperous.
Edited by VicHockeyFan, 12 March 2018 - 07:38 AM.