Zip Code Data Sources

     The data sources for the zip code information here comes from the U.S. Census Bureau's "U.S. Gazetteer" files. These include a central latitude and longitude for each zip code. There are several differences between the two data sets, which the Census Bureau says they have no plans to document. From what I can gather, there were a number of zip codes which were eliminated from the 2000 data -- primarily corporate zip codes and P.O. boxes. In addition, the formula for longitude and latitude seems to have been updated (and presumably improved).

     I use the 2000 data but also include zip codes found in the 1990 data which were eliminated from the 2000 data set.

     The ZCTA file contains data for all 5 digit ZCTAs in the 50 states, District of Columbia and Puerto Rico as of Census 2000. It includes 33,233 such ZCTA's -- though 1152 of these are special "XX" and "HH" codes for land and hydrographic areas not covered by standard zipcodes. Thus there are 32,081 zipcodes included. The file is plain ASCII text, one line per record.

• Columns 1-2: United States Postal Service State Abbreviation
• Columns 3-66: Name
• Columns 67-75: Total Population (2000)
• Columns 76-84: Total Housing Units (2000)
• Columns 85-98: Land Area (square meters)
• Columns 99-112: Water Area (square meters)
• Columns 113-124: Land Area (square miles)
• Columns 125-136: Water Area (square miles)
• Columns 137-146: Latitude (millionths of a degree)
  The first character is blank or "-" denoting North or South latitude respectively.
• Columns 147-157: Longitude (millionths of a degree)
  The first character is blank or "-" denoting East or West longitude respectively.

     The place file contains data for all Incorporated and Census Designated places in the 50 states, the District of Columbia and Puerto Rico as of the January 1, 2000. The file is plain ASCII text, one line per record.

• Columns 1-2: United States Postal Service State Abbreviation
• Columns 3-4: State Federal Information Processing Standard (FIPS) code
• Columns 5-9: Place FIPS Code
• Columns 10-73: Name
  This includes the place name generally ending with a place type : city, CDP, town, village, or borough ("zona urbana" or "comunidad" in Puerto Rico).
• Columns 74-82: Total Population (2000)
• Columns 83-91: Total Housing Units (2000)
• Columns 92-105: Land Area (square meters)
• Columns 106-119: Water Area(square meters)
• Columns 120-131: Land Area (square miles)
• Columns 132-143: Water Area (square miles)
• Columns 144-153: Latitude (decimal degrees)
  First character is blank or "-" denoting North or South latitude respectively
• Columns 154-164: Longitude (decimal degrees)
  First character is blank or "-" denoting East or West longitude respectively

     This is a data set of zip codes from the 1999 census. It includes zip codes from all 50 states, District of Columbia and Puerto Rico. The zip codes include 9749 P.O. boxes and 29915 unique zips assigned to large corporations or government agencies, but it excludes APO/FPO military zip codes. There are a total of 42,192 zip codes (including 29,915 non-P.O., non-unique codes). The original files is a DBF format dBase file, but I have converted it to an SQL dump file and ASCII text format.

• Zip Code
• Latitude, including 6 decimal places
• Longitude, including 6 decimal places
• Zip Class:
  "M" for APO/FPO military zip (none), "P" for P.O. box, "U" for unique zip assigned to large corporations or government agencies, and blank for non-unique zips.
• State FIPS Code
• County FIPS Code
  For zip codes which cross county boundaries, the Post Office file assigns that zip code to just one of the counties rather than each county.
• IDMARPLOT
  A variable used by the LandView4 program.

     The 1990 Zip Code by State file is comma separated values, ASCII text, one record per line. It includes 29470 zip codes. The field/record layout is as follows:

• Field 1 - State Fips Code
• Field 2 - 5-digit Zipcode
• Field 3 - State Abbreviation
• Field 4 - Zipcode Name
• Field 5 - Longitude in Decimal Degrees (West is assumed, no minus sign)
• Field 6 - Latitude in Decimal Degrees (North is assumed, no plus sign)
• Field 7 - 1990 Population (100%)
• Field 8 - Allocation Factor (decimal portion of state within zipcode)