40 C.F.R. § 81.69
The Paducah (Kentucky)-Cairo (Illinois) Interstate Air Quality Control Region is revised to consist of the territorial area encompassed by the boundaries of the following jurisdictions or described area (including the territorial area of all municipalities (as defined in section 302(f) of the Clean Air Act, 42 U.S.C. 1857h(f) ) geographically located within the outermost boundaries of the area so delimited):
In the State of Illinois: Alexander County, Johnson County, Massac County, Pope County, Pulaski County, Union County.
In the State of Kentucky: Ballard County, Caldwell County, Calloway County, Carlisle County, Christian County, Crittenden County, Fulton County, Graves County, Hickman County, Hopkins County, Livingston County, Lyon County, Marshall County, McCracken County, Muhlenberg County, Todd County, Trigg County.
40 C.F.R. §81.69