Wow, I have to say that this is pretty much what I suspected. Given that I've lived all over, I would consider myself a General American English speaker (I aspire to that anyway) but when I hear myself speak, there's a bit of midwestern something in there. I wouldn't call it upper midwestern but since they are calling Dixie, "Dixie", I assume that Oklanhoma, Kentucky, etc., are considered midwestern, so maybe Chicago is "upper". Thanks to my mom (pronounced like "mahm") for the 5% Dixie. And I assume all you New Yawkers are Yanks....I've never associated myself with that term, even when I was told to my face that I am one (in the South, it's everyone who isn't southern). I think there's more than simple geography in those categories.
via Scott atTales from the Sharpside