The Eastern Washington-Northern Idaho 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 Idaho: Benewah County, Kootenai County, Latah County, Nez Perce County, Shoshone County.
In the State of Washington: Adams County, Asotin County, Columbia County, Garfield County, Grant County, Lincoln County, Spokane County, Whitman County.