You have to buy it online and you cannot buy daily passes. At least that was the case when I bought mine. You have to buy the one for the whole year. I believe that's around $40. If you go online it has very detailed information on how to do everything
I purchased one at the Ranger station since it was staffed. I've heard their hours are restricted so online is the safest way to go. https://dnr.wisconsin.gov/topic/parks/admission
You have to buy it in advance, online, before entering the park. Rangers are not there to sell park stickers in person. The cost depends on if you buy a day or year sticker.
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