In the early 1800s, prior to European settlement, tall grass prairie and eastern deciduous forests were the dominant features on the Illinois landscape (Illinois State Nat. Surv. Div. 1960). Forests during this period spanned an estimated 13.8 million acres, approximately 40 percent of the total land area. For nearly 120 years (from 1800 to the 1920s), forest area declined and in 1924 reached its lowest point with only 3 million acres of forest land (Telford, 1926). A survey of Illinois‘ forest resources in 1948 revealed an increase to 4 million acres. Since 1948, forest land has steadily risen and is currently an estimated 4.5 million acres.

Today, most of Illinois' forests are in the southern part of the state. About 80% of that forestland is held by private landowners. There are also significant forested areas in the western portion of the state along the borders of the Illinois and Mississippi Rivers.

Occupying 65 percent of forest land, oak/hickory is the predominant forest-type group in Illinois. Though oak/hickory is found throughout the State, this forest-type group is highly concentrated in west-central and southern Illinois. Elm/ash/cottonwood, which makes up 23 percent of forest land, is the second largest forest-type group.