40 CFR § 81.86 - Metropolitan Sioux City Interstate Air Quality Control Region.

The Metropolitan Sioux City Interstate Air Quality Control Region (Iowa-Nebraska-South Dakota) 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 Iowa: Plymouth County, Sioux County, Woodbury County.

In the State of Nebraska: Dakota County.

In the State of South Dakota: Union County.