40 C.F.R. § 81.81
The Merrimack Valley Southern New Hampshire Interstate Air Quality Control Region (Massachusetts-New Hampshire) 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 Massachusetts: In Essex County, the towns of-Andover, Amesbury, Boxford, Georgetown, Groveland, Haverhill, Lawrence, Merrimac, Methuen, Newbury, Newburyport, North Andover, Rowley, Salisbury, West Newbury.
In Middlesex County, the towns of-Ayer, Billerica, Carlisle, Chelmsford, Dracut, Dunstable, Groton, Littleton, Lowell, Pepperell, Tewksbury, Tyngsborough, Westford.
In the State of New Hampshire: The counties of-Belknap, Cheshire, Hillsborough, Merrimack, Rockingham, Strafford, Sullivan.
40 C.F.R. §81.81