1 county-level rule, plus city-specific rules for 1 city in Winnebago County, Illinois.
Verified from official government sources
Illinois has no statewide ADU mandate - the Counties Code (55 ILCS 5) and Municipal Code (65 ILCS 5) leave ADU regulation to local zoning. Winnebago County permits 'accessory living quarters' under the Unified Development Ordinance (Chapter 90, Article 18) in unincorporated areas, with floor area between 300 and 900 sq ft. Properties inside Rockford, Loves Park, Machesney Park, or other municipalities follow their own zoning codes, not the county UDO.
1 cities in Winnebago County have their own accessory structures rules. Each link goes to that city's dedicated page with code citations.
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