Wis. Stat. § 75.09: Notice, how posted.

If no newspaper be published in such county the county treasurer shall also, at least 3 months previous to the time limited for the redemption of any lands subject to a tax certificate, cause to be posted up copies of the list and notice specified in s. 75.07 in at least 4 public places in the county, one of which copies shall be posted up in some conspicuous place in the treasurer’s office.