Dating back to 1920, Backbone is the oldest state park in Iowa, which makes it the "backbone" of outdoor fun. Actually, the name comes from a rocky ridge known as "Devil's Backbone."
Located in Dundee, the park features more than 2,000 acres in which to play, with activities such as swimming, canoeing, biking, climbing and hiking. Fishermen also enjoy Backbone for its trout-stocked streams (April through October).
Runner-up: Maquoketa Caves State Park