CGs Near Osseo/Eau Claire, WI w/o Minimum Stay Requirement?

On our trip last year couple of campgrounds did have that rule, but if you don't make reservations and keep an eye on the number of open sites, walk ins are not required to book two days if there are nay openings. And if passing through we just had to have that campground for one reason or another just pay for two & leave when you must. I know it isn't the most economical way to do things but it works.