The Allerton Park Trail Run is a 5.7-mile trail race held at Robert Allerton Park near Monticello, Illinois, around Halloween. The course runs alongside the Sangamon River within the 1,517-acre park, offering a genuine trail experience with exposed roots, ruts, sharp turns, and uneven terrain demanding runner focus. A non-competitive 2-mile nature walk is also available, without awards, alongside a virtual option for those unable to attend.
The Second Wind Running Club organizes the race, which concludes in a meadow. Costumes are encouraged because of the Halloween timing. The event features overall, masters, and age-group awards, plus door prizes and costume contest awards. Proceeds from the race support Allerton Park; past contributions have funded a railing at a hazardous location, trail erosion management, recycling receptacles, a water fountain with bottle filling, and enhancements at the visitor center. The park's history predates typical race venues: Robert Allerton bequeathed the estate to the University of Illinois, it is listed on the National Register of Historic Places, and the Allerton Natural Area is a National Natural Landmark.