Menzl - I am not sure why. I would say most of WI has a strong German population. Milwaukee and Green Bay cities as well as the west side of the state. It could simply be the political unrest you had and the fact that WI became a state in 1848. There certainly were people here earlier, but I have to imagine once people saw the land in WI without a million rocks like you see in New England area of the USA, that was attractive. The state like I am guessing most others have many areas of populations that came from a lot of different areas in Europe. I will say that there isn't much of an Italian, Irish or Spanish influence in WI. Mostly German, Dutch, French, British, Polish.
Thank you for the information on political unrest. Good to know and helps put things in perspective.