Enormous Dialect Map of North America

The guy who stars in the documentary American Movie talks a lot like Francis McDormand's character in Fargo. But he was born and raised in Milwaukee which shares accent space with Chicago and upstate New York, and not northern Minnesota.

Perhaps there is a simple explanation for this, but I don't know what it is. My assumption is that it has something to do with social class. Sort of how like southern-like accents seem to exist among poor white people all over the country; and southern-like ebonics is a trans-regional black accent.

Being born and raised in San Francisco, mainly in the '50s and '60s, I picked up some very peculiar ways of pronouncing various words. I didn't realize this till I move to North Idaho. It was in Idaho that I realized that San Francisco is basically a cross section of the world with its many cultures, maybe for only one block, but with foods, language, etc. -- at least that was how it was back in the '50s and '60s.

At various times in my life I've had people ask me where I was from, even when I lived in San Francisco, and when I told them they'd tell me they thought I was from, the Mid-West, New York, Texas, New England, and many other places.

It was a woman here in Idaho that pointed out just how I would pronounce certain words, such as: water, daughter, and quarter. She pointed out that they all sound the same and she would laugh hysterically every time I would say the following: Here's a quarter for the water for your daughter.

May be that is why some people thought I lived over on Tirty-Tird & Tird in the Bronx?

1) There's a ton of detail on that map. I wonder how much of it is empirical data, and how much of it is fantasy... (For example, that On/Dawn/Don distinction for the SF Bay Area? I've lived in this area for 20 years, now, am not a native, and have never heard the middle pronounced any differently than the others, except by out-of-towners.)
2) Really? People in Southern Utah sound the same as people in Seattle?

Man, this is impressive, but I'd really like to know which bits to accept as truth... (And RAF, I don't think Moon Unit was ridiculing the accent she and her friends used. She was documenting it with exaggeration.)

what i'm always puzzled by is the near universal adoption of the "valley girl" dialect by high school and college women...didn't anybody ever hear the scathing zappa song ridiculing that accent?

Yikes, ugly clutter colors! :/