This smooth brew was a common offering around the state before the proliferation of modern coffee machines. You can still find it, if you know where to look.
Are you asserting that it's a tradition that's not limited to Minnesota, or that it's not a tradition that exists in Minnesota?
The article itself isn't archived, it was written recently. I just included an archive link in case anyone hits a paywall on the main link. What is poorly written about it?
EDIT: Are you confusing Vietnamese egg coffee and Swedish egg coffee? They're very different things, and Swedish egg coffee is a Minnesotan tradition. The article explains how it was likely brought over by Swedish immigrants, and then died out in Sweden when filters were invented