105 ILCS 5/3A-1

Each county of the State shall, except as otherwise provided in this Article, be designated as an educational service region, referred to in this Article as a "region". Beginning the first Monday of August, 1995, that portion of a Class II county outside a city of at least 500,000 shall constitute a region. References in this Code to a county as a region shall also mean a portion of a county as a region when appropriate.