Developers

The Census Geocoder is maintained by the Geography Division.

Here is a brief overview of this service:

The Census Geocoder is an address look-up tool that converts your address to an approximate coordinate (latitude/longitude) and returns information about the address range that includes the address and the census geography the address is within. The geocoder is available as a web interface and as an API (Representational State Transfer - REST - web-based service).

The tool allows you to look-up a single address or batch submit up to 1,000 addresses at a time.

GeoLookup results can also be obtained directly by searching on the latitude/longitude coordinates

The information in the geocoder comes from our MAF/TIGER database, which holds our geographic information used for censuses and surveys. The address ranges used in the geocoder are the same address ranges that can be found in the TIGER/Line Shapefiles which are derived from the Master Address File (MAF).

When geocoding your address, you need to select a benchmark (time period) and select a vintage of geography. The benchmark is the time period when we created a snapshot of our data (generally done twice a year). For example, Public_AR_Census2010 is the snapshot we took of the database in 2010. Public_AR_Current is the most recent snapshot we took of our dataset. The vintage of geography is the census or survey that the data relates to. For example, Census2010_Census2010 are the address ranges from the 2010 Census at the time of the 2010 Census. You can also obtain the 2010 Census address ranges as of our 2013 benchmark. The vintages you see available depends on the benchmark you selected.

There are limitations to the address ranges found in our MAF/TIGER database. The address ranges are potential address ranges, not actual address ranges. Potential ranges include the full range of possible structure numbers even though the actual structures might not exist. The majority of the address ranges we have are for residential areas. There are limited address ranges available in commercial areas. Our address ranges are regularly updated with the most current information we have available to us.

Addresses should be formatted in a single line with comma delimiters. The address should consist of:

• Unique ID,
• House Number and Street Name,
• City,
• State,
• ZIP Code

City and State, or ZIP Code may be left blank, but there must be the appropriate number of commas to represent the blank data, for example:

• 1, 1600 Pennsylvania Ave NW, Washington, DC,
• 2, 1600 Pennsylvania Ave NW, , , 20502

are both valid entries, while:

• 3, 1600 Pennsylvania Ave NW, Washington, DC
• 4, 1600 Pennsylvania Ave NW, 20502

are both invalid entries.

The geocoder takes the address and determines the approximate location offset from the street centerline. An interpolated latitude/longitude coordinate is returned along with the address range the Census Bureau has on that stretch of road. That coordinate is then used to determine the geography that the address is within.

List of descriptive names for fields in the results

Using the batch submission, results can be:

• Match/Exact
• Match/Non-Exact
• Tie
• No Match

If a Tie is encountered, there are multiple possible results for that address. The address can be input for single address geocoding to view the multiple results.

Using the web interface "Find Locations Using" option, the results include the estimated latitude/longitude coordinate, TIGER identifier of the street, and full address range on the road segment.

Using the web interface "Find Geographies Using" option, results are returned for the State, County, Census Tract, and Block the address is located within. In addition, attributes of these pieces of geography, such as an urban/rural indicator are included. To see the all of the geography available for the selected address for the time period you selected, type &layers=all at the end of the URL once you get your results back, and refresh the page.

Using the API single record search, any geography that is available for that benchmark/vintage combination in our TIGERweb application can be returned by using the layer code lists in your API request. See the documentation section for additional information.

Using the batch submission, the state, county, census tract, and block codes are returned.

• List of descriptive names for fields in the results
• Using the API [PDF <1.0 MB]
• List of Layer Codes for returning different geography in results

Q. How many addresses can I geocode at one time?

A. Up to 1,000

Q. What is the source of your address ranges?

A. The address ranges used in the geocoder are the same address ranges that can be found in the TIGER/Line Shapefiles which are derived from the Master Address File (MAF). The address ranges are potential address ranges, not actual address ranges. Potential ranges include the full range of possible structure numbers even though the actual structures might not exist. The majority of the address ranges we have are for residential areas. There are limited address ranges available in commercial areas. Our address ranges are regularly updated with the most current information we have available to us.

Q. What vintage geography can I get locations for?

A. 2010 Census, 2012 American Community Survey, 2013 American Community Survey, and Current (half the year current is the same as the most recent American Community Survey).

Q. How do I format my address(es) for use in the geocoder?

A. Addresses should be formatted in a single line with comma delimiters. The address should consist of:

• Unique ID,
• House Number and Street Name,
• City,
• State,
• ZIP Code

City and State, or ZIP Code may be left blank, but there must be the appropriate number of commas to represent the blank data, for example:

• 1, 1600 Pennsylvania Ave NW, Washington, DC,
• 2, 1600 Pennsylvania Ave NW, , , 20502

are both valid entries, while:

• 3, 1600 Pennsylvania Ave NW, Washington, DC
• 4, 1600 Pennsylvania Ave NW, 20502

are both invalid entries.

Q. What coordinate system are the latitude and longitude values?

A. Our latitude and longitude coordinate system is NAD83.

Q. What options do I have if my address isn’t found?

A. Our address ranges consist mainly of residential addresses. If you do not get a result and you know the approximate location of the address, we recommend you use our TIGERweb interactive map viewer. If you do not know the approximate location we recommend you use outside sources to determine the approximate location. We are continually improving our addresses and address ranges. We release updated geography and address ranges at least once per year.

Please send any questions or comments to geo.geocoding.services@census.gov.

Detailed documentation for the Geocoding services can be found here [PDF <1.0 MB].

An Excerpt from that documentation:

Geocoding is the process of taking an address and returning an actual or calculated latitude/longitude coordinate. Depending on the parts of the address that are provided, determines to what granularity it is possible to geocode.

The current Geocoding Services engine requires a structure address be provided. The resulting lat/long is  calculated along an address range.

There are two entry points for the geocoding service – single record submission and batch. The acceptable input address parts are:

• Structure number and street name (required)
• City name (optional)
• State (optional)
• ZIP code (optional)

The single record service allows for all of these parts to be submitted in a single line, or as separate fields.  The batch requires each field to exist (either with text or blank) in a delimited form, preceded by a unique  ID.

This document is intended for application, website, and mobile developers within the U.S. Census Bureau and the general public who want to leverage the Geocoding Services capability.

This service is designed for coding a provided address, or file of addresses, to a latitude/longitude coordinate based on data that’s been loaded into the geocoding engine from a MAF/TIGER benchmark database.

The optional inclusion of the Geographic Lookup (geoLookup) adds information to the result relating to various levels of geography that cover the afore mentioned latitude/longitude coordinate. GeoLookup results can also be obtained directly by searching on the latitude/longitude coordinates.

Please refer to the full specification here: geocoding.geo.census.gov/geocoder/Geocoding_Services_API.pdf