We stayed near a 150-year-old cabin in the woods (see pix below) at Fern Hollow in Decorah earlier this month. (We were in the newer house, in a lovely room made of wood so it felt like a cabin.)
But I was also trying to remember the name of some other options when the DM Register came to the rescue so for future reference here they are:
The Natural Gait http://www.thenaturalgait.com near Marquette, along the good-for-canoeing Yellow River. (I’d heard of this one!) It’s a wildflower farm withe horse stables and a bunch of cabines.
Whiterock Conservancy near Boone – this is the old Garst place which we stayed (in the more gentile Hollyhock Cottage, not the River Cabin) at with our kids (and wrote about for the NYTimes travel section.)
Pinicon ridge Park near Central City, north of Cedar Rapids, – four cabins along a river with one of my favorite names – the Wapsipinicon. Three have heat and AC. The River Otter Cabin is more rustic.