There are so many amazing flea markets in Wisconsin but I want to focus on the humdrum flea markets my mother used to take me to as a kid. I grew up in Wisconsin and they are abundant.
The basic city flea market is usually in some big building in a fairgrounds that is saved for the county fair. You go in and pay a small admission fee that goes to the up keep of the grounds; then you head inside the building where there are stations full of personal craft projects that people are trying to peddle as art.
There was once an entire booth dedicated to beer can wind chimes. As a teenager I was horrified at the tackiness of it. As an adult, I'm still horrified, because who would buy that?
When I went home for my father's funeral and to clean up his house, I stopped in at a flea market on the weekend for nostalgia-sack. People came in droves to see the junk!