40 C.F.R. § 81.60
The Duluth (Minnesota)-Superior (Wisconsin) Interstate Air Quality Control Region has been 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 Minnesota: Aitkin County, Carlton County, Cook County, Itasca County, Koochiching County, Lake County, St. Louis County.
In the State of Wisconsin: Ashland County, Bayfield County, Burnett County, Douglas County, Iron County, Price County, Rusk County, Sawyer County, Taylor County, Washburn County.
40 C.F.R. §81.60