"He changed is name Harry Gibbs and I was trying to figure out how and when he did this."
How: Well, basically, before there were all sorts of official forms of identification, people just stopped using one name and started using another.
When: You need to put together a timeline showing all the documents you've already amassed, their dates, locations, and what name he used on each. (My earlier message suggested the value of this ...) Then you'll need to find documents that fill in the blanks in the timeline (birth records of children, school records, military records, court records, newspaper articles, city directories, property records, obituary, etc.)
You've said he was born in Michigan and married in Minnesota. It's not at all clear what his link to Wisconsin is, and what Wisconsin records might exist for him. If he just breezed through the state, it's not likely that there would be any. But that's hard to know, since you don't state where he was living in the 1930-1940 censuses, or what his residence was listed as on his marriage record (what year was that?).