Elroy-Sparta State Trail is a 33.9 mile lightly trafficked point-to-point trail located near Sparta, Wisconsin that features beautiful wild flowers and is rated as moderate. The trail offers a number of activity options and is best used from March until November.
Helpful tidbit: bring a flashlight. You'll need it for the long tunnels where you're supposed to walk your bike.
I walked this, and the 400 state trail and more, camping along the way, on a 200 mile walk when I turned 50 in 2005. Met some very nice bicyclists who were doing a large group cross country trip, with a big truck hauling their gear. The tunnels down the road were cool. Small town cafes and taverns yielded some good sandwiches. Nice bike trail, even though I walked/backpacked it.
Road this as a kid as a three day trip.
Went with a group of guys back in 2000. The trail was great and the scenery was awe-inspiring. Great for biking but I wouldn't recommend hiking due to all the mountain bikers. Did about thirty miles of the trail over the weekend.