How are ZIP codes structured?
United States ZIP codes are five numerical digits long. The first digit in a ZIP code represents a defined group of U.S. states. The second and third digits represent a region in that group, such as a large city. To send mail, only the first five digits of the ZIP code are required.
What are the 4 extra digits of a ZIP Code?
ZIP+4 Codes (or ZIP Plus 4 Codes) are the final 4 digits of a full nine-digit ZIP Code. The 9-digit ZIP Code consists of two sections. The first five digits indicate the destination post office or delivery area. The last 4 digits represent specific delivery routes within delivery areas.
How are ZIP Code boundaries determined?
As of 1963, zip codes’ numbers are determined by a few factors: the area, the regional postal facility and the local zone. The first number of the five-digit code signifies the region which the address is located in, a number that grows from the east coast to the west.
Are ZIP codes unique?
There are no duplicate ZIP Codes. There are some ZIP Codes that are multi-part polygons, but those polygons are usually adjacent.
What makes a ZIP code a polygonal area?
Zip codes are NOT considered a polygonal area. Projecting Zip codes to a polygonal area will require you to make an educated guess where the boundary is between one zipcode and the next. ZIP code address data specifies only a center location for the ZIP code. Zip code data provides the general vicinity of an address.
How are zip codes assigned to a ZCTA?
The USPS makes periodic changes to ZIP Codes to support more efficient mail delivery. The Census Bureau uses tabulation blocks as the basis for defining each ZCTA. Tabulation blocks are assigned to a ZCTA based on the most frequently occurring ZIP Code for the addresses contained within that block.
Is the USPS ZIP code the official zip code?
Data users should not use ZCTAs to identify the official USPS ZIP Code for mail delivery. The USPS makes periodic changes to ZIP Codes to support more efficient mail delivery. The Census Bureau uses tabulation blocks as the basis for defining each ZCTA.
How are ZIP code lines related to geographical coordinates?
Just as lines are strings of points along a coordinate plane, ZIP code lines are strings of delivery points in the abstract space of USPS-designated addresses. They are not correlated to geographical coordinates.