Midwestern Literature

At a meetup with some writers on Friday, one of them mentioned going to a talk about Midwestern Literature.  This caught my interest, and she proceeded to be unable to answer any of my questions because "honestly I got there late and missed most of the talk."

Like What is Midwestern Literature?  Does the landscape or the culture have to be the driving force like Garrison Keillor or Carl Sandberg?  Is it just anything set in the Midwest?  Is it the voice?  Like Vonnegut, who wrote Cat's Cradle set mostly in a fictional Caribbean nation, or  Slaughterhouse Five set in Germany and space, but still have a Midwestern voice.

Does it have to be rural, or do things in Chicago and St. Louis count?  Big cities are melting pots with populations that move in from New York or the South with other regional literary traditions that are more cohesive.  The cities have more diversity, and does diversity have a place in Midwestern Literature (because it should)?

Can speculative fiction count?  The Dresden Files in urban fantasy, and Divergent is YA dystopia.  Bone Gap is set in Illinois and has a Midwestern voice, but there's magic corn.  

It doesn't seem like Midwestern Literature is a genre that can be pinned down.  There's so much cultural variation across the region and there's not a uniting force that brigs us together, except maybe shoveling snow?  Corn?  Unsolicited advice to lost tourists?  Saying "Aww, geeze," sighing, and doing the thing even though it's unpleasant?  

I want to know more about this.