On March 1, 2016, Governor Walker signed 2015 Wisconsin Act 219 into law eliminating adverse possession by or against municipalities. In other words, individuals or entities cannot acquire publicly owned land by adverse possession, and likewise municipalities cannot acquire privately owned land by adverse possession. (This also applies to other state or county owned land).
According to the legislative memo accompanying the bill, “The prohibition applies retroactively to adverse possession or use where the current 20 year occupancy requirement has not been met at the time of the effective date of the bill.”
I still see some potential for disputes over borders in cases where it is unclear if the 20 year requirement was met prior to the effective date of the new law.