It started at the University of Wisconsin - Madison. I was an undergrad there at the time and never missed an issue (but unfortunately didn't save them). A few random observations:

* It was a huge hit on campus almost right away, or at least once it found its footing and sensibility - the dry conventions of journalism applied to mundane events.

* The sensibility of The Onion was very midwestern, and specifically "college-town Midwestern slacker". I knew exactly the type of people they had in mind when writing about "Area Man". This article captures that well: https://www.midstory.org/the-onions-midwestern-homecoming/

* I remember thinking that lots of college towns must have a satirical newspaper as good as this. Then when it went national, realizing that it was really something special.