Tar Hollow State Park - Ohio. 25+ miles of hiking trails. Also has mountain bike trails. Backpacker campground by fire tower. Link to park's website: http://www.dnr.state.oh.us/parks/parks/tarhollw/tabid/792/Default.aspx
Last weekend, my family and I had the opportunity to hike in the Opal Creek Scenic Area and Wilderness. It is located east of Salem, in the Willamette National Forest. Opal Creek runs through thousands of acres of protected old growth forest, crisscrossed with over 30 miles of hiking trails.