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ZIP Code Database - Facts & Stats

Area Code NPANXX Database Detailed Specifications

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Detail of Data

Please note: Not every record will have all fields populated

Field Name Description
State Two letter USPS state abbreviation
NPANXX Combined Area Code and local number prefix (six digits)
NPA Area Code (NPA = Numbering Plan Area)
New NPA This field is no longer available.
NXX Three digit local number prefix (X=2-9, X=0-9). Generally 201 thru 999.
Status Indicates if this NPANXX is in active use ("Active" or "Inactive")
Latitude Latitude of record for the central office
Longitude Longitude of record for the central office
WeightLat Latitude for the centroid of the ZIP Code that has the highest frequency of occurrence within the NPANXX
WeightLon Longitude for the centroid of the ZIP Code that has the highest frequency of occurrence within the NPANXX
LATA Local Access Transport Area
City Name Popular or political name of city
Time Zone Offset from GMT (5=East, 6=Central, 7=Mountain, 8=West, etc..)
County Name of county this record resides in.
County Population The population of the county from the 2010 Census.
ZIP Code ZIP Code (United States) (five digits)
ZIP Code Population

Approximate population of the ZIP code.

Zip Code Freq.

Percent frequency of occurrence of this Zip Code in the NPANXX area.

If = 0, then unknown
If = -1, then the ZIP Code is the most frequent, but % unknown
If = -2, then the ZIP Code is the second most frequent, but % unknown

NXX Type Primary use designation. L=Landline, W=Wireless (all wireless; pagers, cellular, PCS, etc.)
Note that some NXXs may be subdivided between landline and wireless. This is simply the reported type.
NXX Intro Version of this product that NXX first appeared. This is not necessarily the NXX service date, but it should be within 12 months. exception: Since 1994-02-04 was the first version that included the intro date, then all older NXXs will have an intro date of 1994-02-04 regardless of actual service date.
Overlay 1 = NPA recent overlay, blank = Not an overlay
Rate Center Ten character Rate Center name for CO. Blank = Rate Center name unknown.
MSA_CBSA Census Bureau Names for the metro area of the central office.
MSA_CBSA_CODE Census Bureau ID numbers for the metro area of the central office.
FIPS Census Bureau FIPS code (ID) for the tract of the central office
Observes DST 1 = Observes DST (Daylight Saving Time) during the normal DST observance period, 0 = Does not observe DST at all. Some areas of the country such as AZ (except for the Navajo Nation), HI, GU, PR, VI, and parts of IN do not observe DST.
OCN Four-character alphanumeric field identifying the NPA-NXX code-holder and/or service provider.
Phone Company The name of the phone company the NPA/NXX is registered to.
CoverageAreaName The name of the area this NPA-NXX Covers. This is primarily the city name
but other Alias Names may be used.

ZIP Code Information

In addition to the actual ZIP Code itself, there are two data fields that help you to determine how relevant the ZIP Code is. The two data fields are:

ZIP Code frequency of occurence

ZIP Code frequency of occurrence means the percent of all listed subscribers within an NPA/NXX that have a particular ZIP Code. ZIP Codes that have a frequency of occurrence of less than 2% are omitted from the data. That's because those ZIP Codes are statistically insignificant and are quite likely better represented in an adjacent NPA/NXX.

While ZIP Code boundaries rarely change and CO boundaries essentially never change, there is little deliberate alignment of those boundaries. Consequently, there's nearly always overlap of ZIP Code between adjacent COs (NPA/NXX). By evaluating the frequency of occurrence, you can determine a ZIP Code's relevance within an NPA/NXX relative of it's occurrence in an adjacent NPA/NXX.


When using the data to match ZIP Codes to NPA/NXXs, you'll want to consider both a reasonable frequency of occurrence and actual ZIP Code count to help you determine the accuracy of the match. Selecting reasonable frequency of occurrence and ZIP Code count values are up to you depending on your application, but the higher the value the more accurate the match.

ZIP Code Sourcing

Some NXXs have detailed ZIP Code data (Level 2, detailed) where detailed data were available. Other NXXs may only show one or two ZIP Codes without a frequency of occurrence (Level 1, not as detailed). Here is the key to values in the frequency of occurrence field.

If the frequency of occurrence is -1 or -2, then the ZIP Code count for this record is meaningless -- ignore it.

nnn where nnn is a positive number between 1 and 100. This is the estimated frequency of occurrence for this ZIP Code.
-1 Most frequently occurring ZIP Code, although percentage is unknown.
-2 Second most frequently occurring ZIP Code, although percentage is unknown.