Postal zones

§ 4553. Postal zones (a) For the purposes of fourth class mail the United States, its possessions, the Territory of Hawaii and the Commonwealth of Puerto Rico are divided into units of area thirty minutes square, identical with a quarter of the area formed by the intersecting parallels of latitude and meridians of longitude, represented on postal maps or plans. (b) The units of area are the basis of eight postal zones, as follows: (1) the first zone includes all territory within the quadrangle in conjunction with every contiguous quadrangle, representing an area having a mean radial distance of approximately fifty miles from the center of a given unit of area. (2) the second zone includes all units of area outside the first zone lying in whole or in part within a radius of approximately one hundred and fifty miles from the center of a given unit of area. (3) the third zone includes all units of area outside the second zone lying in whole or in part within a radius of approximately three hundred miles from the center of a given unit or area. (4) the fourth zone includes all units of area outside the third zone lying in whole or in part within a radius of approximately six hundred miles from the center of a given unit of area. (5) the fifth zone includes all units of area outside the fourth zone lying in whole or in part within a radius of approximately one thousand miles from the center of a given unit of area. 74 Stat. 675 (6) the sixth zone includes all units of area outside the fifth zone lying in whole or in part within a radius of approximately one thousand four hundred miles from the center of a given unit of area. (7) the seventh zone includes all units of area outside the sixth zone lying in whole or in part within a radius of approximately one thousand eight hundred miles from the center of a given unit of area. (8) the eighth zone includes all units of area outside the seventh zone.