The Helena Intrastate Air Quality Control Region (Montana) 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 Montana: Beaverhead County, Broadwater County, Deer Lodge County, Gallatin County, Granite County, Jefferson County, Lewis and Clark County, Madison County, Meagher County, Park County, Powell County, Silver Bow County.