I was told by a Southern lady that when you live in the Deep South, you must speak slowly so that your mouth does not overheat. (Put that in your best Selma, AL accent!)

That doesn't explain the phenomenon of two words becoming one (e.g. Old Bay becomes Olbay, Spring Hill becomes Springill).

I'm kind of obsessed with variations in pronunciation across the US (having lived in no fewer than seven different regions of the US - with seven different accents - and adding in my mom's East Coast accent to make eight.) The Southern lady might actually be on to something, though. If you want a good Fargo/Minnesota accent, go stand in a freezer until your mouth goes numb. Amazing!