Category I areas - high quality remnants of the original natural communities of Illinois
Category II areas - habitats of State listed endangered species of animals or plants
Category III areas - relic species habitat
Category IV areas - outstanding representatives of Illinois' geologic diversity
Category V areas - restorations of the original natural communities of Illinois or relocated populations of endangered or threatened species of animals or plants
Category VI areas - lands or waters supporting unusual concentrations of wildlife and other unique natural areas
Category VII areas - outstanding streams, rivers, and lakes;
Ill. Admin. Code tit. 17, § 4010.150