40 C.F.R. § 81.92
The Monroe (Louisiana)-El Dorado (Arkansas) Interstate Air Quality Control Region consists 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 Louisiana: Caldwell Parish, Catahoula Parish, Concordia Parish, East Carroll Parish, Franklin Parish, Grant Parish, La Salle Parish, Madison Parish, Morehouse Parish, Ouachita Parish, Richland Parish, Tensas Parish, Union Parish, West Carroll Parish.
In the State of Arkansas: Ashley County, Bradley County, Calhoun County, Nevada County, Ouachita County, Union County.
40 C.F.R. §81.92