Spitler Woods State Natural Area, a 200-acre site in Mt. Zion in Macon County, is home to one of the largest acreages of old growth woods in central Illinois. Much of the site is dedicated as Spitler Woods Nature Preserve, providing additional protection for the site's valuable natural features.
Spitler Woods mesic upland forest includes red oak, sugar maple, black walnut and basswood on the hillsides and slopes. Dry mesic forest containing white oak, red oak and shagbark hickory is present on the higher elevations. Wet-mesic floodplain forest containing sycamore, hackberry and Ohio buckeye