Illinois tribes of native Americans inhabited the region until 1730 when the Sauk and the Fox tribes, who were being forced westward by the colonists, invaded and inhabited the region. The Native Americans called the river in the new territory "Sinnissippi," meaning "rocky waters."
In the early 1800s, the native Americans were again forced westward into Iowa. In 1831, Blackhawk, the Sauk chief, led his people in a series of raids back into Illinois to reclaim their ancestral lands. The battles that followed were known as the Blackhawk Indian wars. Chief Blackhawk was captured in 1832 and ordered to a reservation.
The Castle Rock area was settled by New Englanders early in the 19th century. This area was proposed as a state park in 1921 by the "Friends of Our Native Landscape," who acquired some of the land they described as "a unique wilderness remnant of great natural beauty and scientific interest." In 1964, the Natural Lands Institute, a non-profit natural lands preservation group, conducted a public fundraising campaign to preserve part of the Castle Rock area.
Castle Rock was recognized in Illinois as an outstanding area of major scientific importance in 1965. It was established as a project area, and land acquisition by the State of Illinois started in 1970.
At the present time, Castle Rock consists of approximately 2,000 acres, 710 of which are designated as an Illinois Nature Preserve. The site was dedicated as a state park in 1978.
Natural Features and Nature Preserve
The basis for the acquisition of Castle Rock State Park is the protection of natural resources unique to Illinois. A thin layer of glacial till covers this region and several distinctive plant species, remnants of the native forest and prairie, still exist. In one valley, 27 different types of ferns have been identified. The park is one of the largest significant natural areas in the northern part of Illinois.
Most of the outstanding natural features are located in the dedicated Nature Preserve which is protected by state law. Use of the 710-acre preserve is restricted to scientific study and limited interpretation activities.
The planned development of Castle Rock centers around the Nature Preserve. All development is limited by soil types. Soil types consist of silt loams and fine, sandy loams which are connected with the general high degree of slopes, which help to limit use and development at Castle Rock. These soils are subject to severe erosion under heavy use.
Castle Rock is a large sandstone butte situated between the Rock River and Ill. Rt. 2. The rock is made up of St. Peter sandstone. In only a few places in Illinois does St. Peter sandstone comes to the surface, even though it underlies practically the entire state.