The US EPA didn’t put who counties on the list; just certain zip codes.
As I remember the fight over state legislation requiring vehicle emission testing only zip codes on the eastern edge of McHenry County were inclluded.
Investigation found that the reason for the listing didn’t have a lot of science behind it.
I’m remembering a testing station just over the Illinois-Wisconsin state line that led to our being designated a nonattainment area.
The only result that most people saw was the requirement to have one’s motor vehicles tested for emission compliance.
It also led to people living in the designated areas to register cars that were not “clean enough” to find addresses in places like Wonder Lake, which testing was not required.
It is conceivable that companies with pollution problems wanting to locate in the Chicago Metropolitan Area selecting McHenry County.
The Illinois EPA has not figured out what this means to McHenry County and a little county on the edge of the Metro-East area called Monroe.