I was researching the glacial edges, there are some blank spots in WI and I didn't pay so much attention, being in IA.
If you do the research I think you'll find references to gold there, how much and where, anybodies guess. North central and north eastern IA had a 'rush' and is stated that an Oz. a day was to be had. Every time I had a plan to go up that way it would rain all week bringing highwater, to the point that I just started believeing God wanted me to use a metal detector.
Research with the historical society to see what areas had gold or boomed due to mini- rushes if there were any. Worse comes to worse, you can come over here and look for it. NE IA looks dang promising, other places too. I'd bet money there's gold over your way. An Oz. a day anywhere around here or even on the average out west is pretty iffy.