Understanding Esri U.S. Geography
Learn about the collection, coverage, and structure of the geographic layers used to summarize Esri’s curated demographic content.
Esri Demographics contain a broad collection of demographic content for the United States and the territory of Puerto Rico. Data are available in both Census-maintained statistical and administrative boundaries, as well as other non-Census boundary layers. This tutorial will spotlight the geographic layers, their purpose, and how they do and don't relate to each other.
In this tutorial, you will learn about the following:
- How each geographic type is defined, including the coding structure that uniquely identifies geographic entity within a layer;
- The Esri tools used to summarize data for custom geographic polygons;
- How to access map layers with Esri Demographics.
First, you will learn about Esri geography and the types of geographic layers available.
What is Esri Geography?
"Geography is the science of our world. And it’s an organizing principle for all other sciences. You can overlay biology on top of geography, overlay human patterns like land uses or where different people live on top of geography. You can see it all together as an integrated whole." - Jack Dangermond, Esri President
What geographic layers are available?
Esri Demographics for the United States are available for 11 geographic layers: Nation, State, County, Tract, Block Group, Place, Congressional District, Core Based Statistical Area (CBSA), Designated Market Area (DMA), and ZIP code. At the core of the geography stack is the standard Census Bureau hierarchy: Nation, States, Counties, Tracts, Block Groups, and Blocks. The lowest level of Census geography (blocks) is used within Esri software for data apportionment to produce summary estimates for custom areas. The chart below illustrates the relationship between the boundaries.
Let's learn more about each type, starting with the Census nested hierarchy:
The Nation is the broadest geographic level for the United States covering the 48 contiguous states, Alaska, Hawaii, District of Columbia, and Puerto Rico (not shown).
All 50 states and the District of Columbia are identified by a two-digit Federal Information Processing Series (FIPS) Code and assigned alphabetically based on the state name. The Census Bureau treats Puerto Rico (FIPS 72) as a state for the purpose of presenting data.
Let’s choose the state of Texas to illustrate the top down progression of the nested Census boundaries--from state to block--and explain the geographic coding structure used for each layer.
These codes work together to easily distinguish areas throughout the U.S. From the previous FIPS Code chart, the geographic code for Texas is 48.
Most states are subdivided into administrative or political areas called Counties (or equivalent areas). Texas is comprised of 254 counties.
In Alaska these equivalent geographic divisions are referred to as boroughs, city and boroughs, municipalities, or census areas. In Louisiana, these areas are called parishes. The District of Columbia, a state equivalent, is not further divided by county but also treated as a county equivalent for statistical purposes.
Maryland, Missouri, Nevada and Virginia have incorporated places that are not part of a county and are treated as county equivalents.
In Puerto Rico, county equivalents are called Municipios.
Every county (or equivalent area) is assigned a unique five-digit code where the first two digits represent the state FIPS followed by a three-digit county code that is assigned alphabetically within each state.
Shown right is the county boundary for Travis County, Texas, while the chart below shows its county's geographic code.
Counties do not cross state boundaries.
The next level of geography, Census Tracts, are statistical subdivisions of counties or county equivalents as defined by the Census Bureau and its local stakeholders.
The size of a tract is defined by settlement density and partitioned using the physical landscape or legal boundaries. From Census 2020, a typical tract will contain around 4,000 persons but generally vary between 1,500 to 7,000 persons, as per the 5th and 95th percentiles of the distribution.
Census tracts are identified by an eleven-digit code. Some times this code may include a decimal separator between the ninth and tenth digit. The first five digits of a tract code begins with the two-digit state FIPS and three-digit county code followed by six digits identifying the tract portion of the full code (ex: SSCCCTTTT.TT, where S=state, C=county, T=tract).
Shown right is a census tract located in Travis County, while the chart below shows its geographic code:
Tracts are non-overlapping and wholly contained within county, and state boundaries.
Census tracts are further subdivided into areas called block groups, which are comprised of a collection of blocks. As with tracts, these areas are defined by the Census Bureau along with local stakeholders. From Census 2020, a typical block group will contain around 1,300 persons but generally vary between 600 to 2,600 persons, as per the 5th and 95th percentiles of the distribution.
The first five digits of a block group code begins with the two-digit state FIPS, the three-digit county code, the six-digit tract code, followed by one digit identifying the block group (ex: SSCCCTTTT.TTB, where S=state, C=county, T=tract, B=block group). Block groups with a "0" code represent all-water block groups.
Shown right, Census Tract 48453001914 is comprised of 5 block groups, with corresponding FIPS codes ranging from 484530019141 through 484530019145. Below shows the geographic code for one block group.
Block groups are non-overlapping and wholly contained within tract, county, and state boundaries.
The last component of the nested layers are Census Blocks. This is the Census Bureau’s most granular geographic area. Blocks are generally small in area, particularly in urban areas. However, blocks in rural or remote areas may cover hundreds of square miles.
The Census Bureau establishes these statistical areas that are typically bounded by visible features that are incorporated in this process such as streets, rail lines, hydrological features, and so on. A group of blocks forms the higher level of block group. There are 8,132,968 blocks in the Census 2020 geography, compared to 8.2 million in Census 2000 and slightly more than 11 million in 2010. Block codes follow the format of SSCCCTTTT.TTBLLL, where S=state, C=county, T=tract, B=block group, L=block.
Within Block Group 484530019143, there are 4 blocks (shown right using a hatched pattern). Each block has a corresponding FIPS code ranging from 484530019143001 through 484530019143004. Below shows the geographic code for one block.
Blocks are foundational layer of the geographic boundaries in this nested stack.
Additional commonly used geographic layers
Esri summarizes demographic data for six other area types that are not part of the above nested hierarchy:
County subdivisions (CSDs) are the primary divisions of counties and include census county divisions (CCDs), minor civil divisions (MCDs), census subareas, and unorganized territories. CCDs exist in 20 states, MCDs are in 29 states plus D.C., while census subareas (CSD equivalents) exist only in Alaska. In Puerto Rico, County Subdivisions are referred to as Barrio, Barrio-Pueblo, or Subbarrio. Some CSDs represent legal entities while others are established by the Census Bureau and local stakeholders for statistical purposes. County Subdivision codes follow the format of SSCCCDDDDD, where S=state, C=county, D=Subdivision. Listed below is the geographic code breakdown for the Austin, Texas CCD:
Places include incorporated places (usually cities, towns, villages, or boroughs), census designated places (CDPs), and balance portions of consolidated cities. Places are always within a single state, but they can and often do cross county boundaries. In Puerto Rico, places are referred to as Zona Urbana and Comunidad. Places are uniquely identified using a two-digit state FIPS code and a five-digit place FIPS code, following the format of SSPPPPP, where S=state, P=Place. Listed below is the geographic code breakdown for Austin city, Texas:
Core-Based Statistical Areas (CBSAs), which include metropolitan and micropolitan statistical areas, are composed of one or more counties and are defined by the U.S. Office of Management and Budget (OMB). A metropolitan statistical area is associated with at least one urbanized area of 50,000 or more inhabitants. A micropolitan statistical area is associated with at least one urban cluster of at least 10,000 people, but less than 50,000. The central counties of a CBSA are included based on population in urban areas while outlying counties are included in the CBSA based on a worker commuting threshold. Principal cities in the name of CBSAs are determined by population and employment thresholds.[1] Listed below is the geographic code for the Austin, Texas CBSA:
Designated Market Areas (DMAs) are television markets defined by The Nielsen Company and are revised on an annual basis. Most DMAs are composed of one or more counties, although a few DMAs include county parts. For the DMAs that split counties, Esri finalizes the DMA boundaries to align with boundaries of block groups. While the vast majority of the United States is covered by a DMA, there is an area in Alaska that is not part of any DMA. The Nielsen Company does not produce DMAs for Puerto Rico. Listed below is the geographic code for the Austin, Texas DMA:
Congressional districts (CDs) are the areas from which individuals are elected to the U.S. House of Representatives. Once the apportionment of congressional seats is made based on census population counts in a state, each state establishes CDs to elect representatives. A congressional district is uniquely identified using a two-digit state FIPS code and a two-digit CD FIPS code: SSDD, where S=state, D=District, where congressional district codes range from “01” to “53”, the code for “At Large” (single district for state) is “00”, the nonvoting delegate code is “98”, and “ZZ” is used for any area not assigned to any congressional district. The District of Columbia and territory of Puerto Rico are assigned a code of 98 to identify their single area, nonvoting delegate status in Congress. Listed below is the geographic code breakdown for Congressional District 21 in Texas:
School districts are geographical areas designated by local or state officials to organize and manage public education within a specific region. The Census Bureau tabulates data products for these areas, largely for use by the U.S. Department of Education. Esri provides three types of school district boundaries: unified, secondary, and elementary . School districts can vary significantly in size, with some serving only a single school and others encompassing multiple schools across a large geographic area. In general, where there is a unified school district, no elementary or secondary school district exists; and where there is an elementary school district, a secondary school district may or may not exist. A school district boundary is uniquely identified using a two-digit state FIPS code and a five-digit school district code and are always within a state.
Listed below is the geographic code breakdown for the Austin Independent School District in Austin, Texas.
Residential ZIP codes are defined solely by the U.S. Postal Service to expedite mail delivery not associated with other geographic layers. Because ZIP code boundaries are not contiguous census geographic areas, or stable over time, data estimated for ZIP codes can also change; sometimes monthly or whenever the U.S. Postal Service revises delivery routes. Residential ZIP code data is estimated from block data established from block group estimates, using a correspondence file created by Esri to assign Census 2020 block points to ZIP code boundaries. Esri updates ZIP codes each year based on the latest boundaries and vintage obtained from TomTom. These boundaries completely cover the U.S. and Puerto Rico, including areas where there is no mail delivery (very remote/rural areas).
No official source for ZIP code boundaries exists. As a result, depending upon the source that created them, differences will exist due to the selection of data inputs and methodological approach used to draw these postal polygons. Moreover, since this inventory is subject to monthly updates by USPS, there can be vintage differences in the boundaries as well. So, it is important to use caution when combining ZIP code summary data from sources outside of Esri Demographics.
Listed below is the geographic ZIP code for Sonora, Texas:
Review and considerations
Be mindful of periodic updates to geographic boundaries. Geographic types like ZIP codes, places, CBSAs, or DMAs change more frequently than others. Learn more about Esri's geographic boundary vintages
Not all Esri Data is available for all geographic levels. Use Esri U.S. data catalogs or view Esri U.S. data fact sheet to learn about data sources, vintage, and updates.
User defined geographic areas
While many analysts use Esri's demographic databases via the aforementioned pre-summarized geographic layers, the derivation of a custom, or user-defined trade area is often required. But these custom boundaries generally do not follow common geographic areas such as census block groups or tracts. Hence, Esri's Enrich Layer tools in ArcGIS Pro, ArcGIS Online, and the GeoEnrichment service deploy a data apportionment algorithm to summarize data to any custom polygon. This technique leverages the underlying Census block centroids to enrich demographic, socioeconomic and business attributes to an input polygon. See more information on this process
Next steps
In this tutorial, you learned about the basics of Esri U.S. Geography -- specifically geographic layers, their purpose, and how they may or may not relate to each other. Additional data tutorials in two series are available. Click the links below for continued data exploration, learning, and ways to access U.S. Updated Demographics.
You can access Esri Demographics using Esri software and through apps like ArcGIS Business Analyst, ArcGIS for Excel, or ready to use maps from ArcGIS Living Atlas of the World. For use outside of the Esri platform data files are available in CSV, dBase, Excel, shapefile, or file geodatabase formats.
Contact an Esri data sales specialist with data questions at 800-447-9778 or send an email with your request to: datasales@esri.com.
Learn more
Data methodologies
Esri Demographic Methodology Statements offer detailed insights into how Updated Demographics databases are created; citing sources and techniques used to compile Esri databases such as population, age distribution, income levels, Tapestry Segmentation, Market Potential, and more.
Frequently asked questions
Use our data reference page to help answer additional questions about Esri Demographics.
Helpful links
Connect with us
If you have a topic you would like covered in a data tutorial to help you better understand U.S. data, send us an e-mail with your topic idea.
About this tutorial
This tutorial was created using Story Maps. All map images used ArcGIS Pro. Listed below are sources used to inspire the content: