Being born in the middle of nowhere in Iowa, I speak pretty fluent corn-ball with a redneck accent......
North Western Pa here and I absolutely have an accent. People here in VT are always asking me where I grew up..In general- OH, MI, and western PA as well as most of the Pacific West typically has far less of an accent that most other places.
At least from my experiences.
I'll add MD and VA as well.
Not here in minnesota!