The question comes up now and then.
Does the Inland Northwest have a distinct accent?
You can mark me down as a skeptic.
Proponents of the idea that there is a unique accent here often point to certain expressions, phrases or grammatical irregularities. But I've never viewed that as synonymous with a true accent. None of that is anywhere near universal here and much of it has more to do with socio-economic background than geographically-determined linguistic heritage.
Besides, every non-Indian in the West is from someplace else, if you go back a few generations. The people who settled here came from the Midwest, the South, the Northeast, the Plains, Canada, Asia -- you name it. That wouldn't seem apt to lend itself to homogenous vocal patterns and quirks.
Due to national mobility, media and other reasons, regional accents are said to be in decline where they actually do exist. But here in West Dakota, I doubt that we ever had one to begin with.