One of the Seven Wonders of Illinois, The Park consists of over 1,500 acres, including the Sangamon River, floodplains, lowland and upland forests, a meadow, a 30-acre demonstration prairie and over 14 miles of hiking trails.
Allerton Park has long been recognized as one of Illinois’ most significant natural areas. It is located in the Grand Prairie Natural Division (Schwegman, et al. 1973) and contains outstanding examples of old-growth floodplain and upland forest. It supports populations of the state endangered eastern massasauga (Sistrurus catenatus), state threatened Kirtland’s watersnake (Clonophis kirtlandii), black-billed cuckoo (Coccyzus erythropthalmus) and Mudpuppy (Necturus maculosus).
Allerton Park is one of only three areas in central Illinois with over 500 acres of contiguous forest. Large forested tracts are important breeding areas for many neotropical migrant birds whose populations have declined dramatically as forest fragmentation has created smaller and more isolated woodlots.
The high diversity of natural communities and native species, especially forest trees and wildflowers, and the park’s location along an unmodified reach of the Sangamon River also contribute to the high natural quality of the site. A portion of the site has been recognized as a National Natural Landmark by the U. S. Park Service.
Allerton natural areas comprise 95% of the Park. They constitute one of the most valuable forests in Illinois.