Illinois' Forest Preserve District Act of 1913 allowed for the creation of Forest Preserve Districts to: 

acquire … and hold lands … containing one or more natural forests or lands connecting such forests or parts thereof, for the purpose of protecting and preserving the flora, fauna and scenic beauties within such district, and to restore, restock, protect, and preserve the natural forests and said lands together with their flora and fauna, as nearly as may be, in their natural state and condition, for the purpose of the education, pleasure, and recreation of the public.

The Forest Preserve District Association, a Chicago-based group which formed in 1911, had pushed for legislation to facilitate protection of natural areas. The first Forest Preserve District established in Illinois was the Forest Preserve District of Cook County, established in 1914.

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Typical Forest Preserve Districts are county agencies supported by local taxation.  Specific Illinois statutes that govern the creation of Forest Preserve Districts are in Chapter 70.  Similar Illinois statutes in Chapter 70 govern the formation of Conservation Districts which serve similar purposes (see the Conservation Districts page for additional information).