[troutman]

https://en.wikipedia.org/wiki/Kootenays

The Kootenays are commonly split either into East and West, or East, Central and West. In general use amongst locals of the area, the "East/West" convention is more common as a descriptor of where someone is from or where a town is located (rather than splitting the region into "East/Central/West" subregions). That being said:

The usual East-West separator is the Purcell Mountains, a range running north/south through the region. Areas to the east of this range are deemed to be in "East Kootenay" or the "East Kootenays" while places west of this division are in "West Kootenay" or the "West Kootenays". This places Creston and points east in the East Kootenay (or East Kootenays) and Crawford Bay, Salmo and points west in the West Kootenay (or West Kootenays).

The usual East-Central-West separators are the Purcell Mountains splitting East from Central and the Selkirk Mountains splitting Central from West.

It remains unclear why both Kootenay and Kootenays are used somewhat interchangeably to describe the area. The plural form is in reference to The Kootenays, both East and West; the singular is in reference to the Kootenay Region. In practice the two terms are used interchangeably, although one indicates a geographical region and the other a legal boundary, the Kootenay Land District, which was identical with the original federal and provincial Kootenay ridings.