Matthiessen State Park is an Illinois state park located a few miles south of the more famous Starved Rock State Park. The main entrances to both parks are located on Illinois State Route 178. The park is near Oglesby, in LaSalle County, Illinois, USA. It is named for Frederick William Matthiessen, who had originally owned the property and managed it as a private park. The area was originally referred to as Deer Park, in reference to the large deer population.