Sec.  73.609   Zones.

   (a)  For the purpose of allotment and assignment, the United States is
   divided into three zones as follows:

   (1) Zone I consists of that portion of the United States located within the
   confines  of  the  following lines drawn on the U.S. Albers Equal Area
   Projection  Map  (based on standard parallels 291/2 ° and 451/2 °; North
   American datum): Beginning at the most easterly point on the State boundary
   line between North Carolina and Virginia; thence in a straight line to a
   point on the Virginia-West Virginia boundary line located at north latitude
   37 °49' and west longitude 80 °12'30"; thence westerly along the southern
   boundary lines of the States of West Virginia, Ohio, Indiana, and Illinois
   to a point at the junction of the Illinois, Kentucky, and Missouri State
   boundary lines; thence northerly along the western boundary line of the
   State of Illinois to a point at the junction of the Illinois, Iowa, and
   Wisconsin State boundary lines; thence easterly along the northern State
   boundary line of Illinois to the 90th meridian; thence north along this
   meridian to the 43.5 ° parallel; thence east along this parallel to the
   United States-Canada border; thence southerly and following that border
   until  it  again intersects the 43.5 ° parallel; thence east along this
   parallel to the 71st meridian; thence in a straight line to the intersection
   of the 69th meridian and the 45th parallel; thence east along the 45th
   parallel to the Atlantic Ocean. When any of the above lines pass through a
   city, the city shall be considered to be located in Zone I. (See Figure 1 of
    Sec. 73.699.)

   (2) Zone II consists of that portion of the United States which is not
   located in either Zone I or Zone III, and Puerto Rico, Alaska, Hawaiian
   Islands and the Virgin Islands.

   (3) Zone III consists of that portion of the United States located south of
   a line, drawn on the United States Albers Equal Area Projection Map (based
   on standard parallels 29.50 and 45.50 North American datum), beginning at a
   point on the east coast of Georgia and the 31st parallel and ending at the
   United  States-Mexican  border,  consisting of arcs drawn with a 241.4
   kilometer  (150 mile) radius to the north from the following specified
   points:
       North latitude West longitude
   (a)      29 °40'00"      83 °24'00"
   (b)      30 °07'00"      84 °12'00"
   (c)      30 °31'00"      86 °30'00"
   (d)      30 °48'00"      87 °58'30"
   (e)      30 °00'00"      90 °38'30"
   (f)      30 °04'30"      93 °19'00"
   (g)      29 °46'00"      95 °05'00"
   (h)      28 °43'00"      96 °39'30"
   (i)      27 °52'30"      97 °32'00"

   When any of the above arcs pass through a city, the city shall be considered
   to be located in Zone II. (See Figure 2 of  Sec. 73.699.)

   [ 28 FR 13660 , Dec. 14, 1963, as amended at  33 FR 15422 , Oct. 17, 1968;  50 FR 23697 , June 5, 1985;  51 FR 44070 , Dec. 8, 1986]