We live not very far from Starved Rock state park in Utica, IL. My wife and I love this park. Located on river Illinois, the park is named after an Indian battle during which a group of Illiniwek took position on top of a high, flat rock formation, was surrounded by the Ottawa and Potawatomi tribes and starved to death.
Despite such sad history, the park is a very pleasant place to visit, especially if you love nature and hiking. 13 miles of hiking trails go through the beautiful forest with creeks, waterfalls, and rock formations similar to the one that has given the part its name. The trails are well marked, you will not get lost. Guided hikes are also available, but my wife and I prefer to be on our own.
As to lodgings, you can stay at Starved Rock Lodge, a very nice hotel with a swimming pool, restaurant, and gift shop. We stayed there once and enjoyed it, although it is rather expensive.