The Pacific Northwest & The Columbia River Basin
The Pacific Northwest can be briefly described as the region drained by the Columbia/Snake River ststem. There is no universal agreement about how far beyond that core area the term is appropriate. Political divisions pull the definition one way, physical geography another.
The Columbia rises in Canada, and so does the Fraser, whose delta occupies the
northern end of Washington’s Puget Sound country. The two rivers follow the
same notable pattern, flowing northwest along the Rocky Mountain Trench before
swinging abruptly south. (The trench continues unbroken from Idaho to Alaska,
the expression of long-term tectonic shifts affecting the entire region).
This map extends up to the headwaters of the Columbia above Banff, east
to the Continental Divide, south into northern Nevada for the southern
tributaries of the Snake, and into California for the southernmost
Included on the map: All of Washington, Oregon, and Idaho, with lots of
British Columbia, Alberta, and Montana.