The Olympic-Northwest Washington Intrastate 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 Washington: Clallam County, Grays Harbor County, Island County, Jefferson County, Mason County, Pacific County, San Juan County, Skagit County, Thurston County, Whatcom County.