One of the largest parks in the state, packed with recreational opportunities.. In Short Shaped by Illinoian and Wisconsinan glaciers, the region is characterized by rolling hills and lush prairie-type flora. The overall appearance of the area drastically changed in 1978 when the U.S. Army Corps of Engineers opened the East Fork Reservoir as part of its flood-control program. East Fork's large camping areas offer electrical hook-ups, showers, flush toilets and boat ramps. Hikers will delight in the the Backpack Trail and the 37-mile Steven Newman Worldwalker Perimeter Trail, along with numerous shorter trails.