The United States Census Bureau is the main provider of population and geographic data in the U.S. It runs the national census every 10 years. But it also provides regular data updates through other surveys.
If you work in GIS, especially on projects in the U.S., Census Bureau data is essential. It helps you understand where people live, how they live, and how that’s changing over time.
What Is the Census Bureau?
It’s a federal agency under the U.S. Department of Commerce. Its job is to count the population and collect data about housing, economy, and communities. The decennial census is its most well-known product. But it also runs many other programs that feed data into maps, reports, and decisions. All data is public and free to use.
Key Census Bureau Programs for GIS
Decennial Census
- Happens every 10 years (most recent in 2020).
- Counts every person living in the U.S.
- Provides data on age, sex, race, household size, and housing.
- Most detailed geographic coverage—down to the block level.
American Community Survey (ACS)
- Ongoing survey with annual updates.
- Covers education, income, language, housing, jobs, commuting, and more.
- Provides 1-year and 5-year estimates.
- Used heavily for planning and analysis between censuses.
TIGER/Line Files
- Shapefiles of geographic boundaries.
- Includes states, counties, cities, census tracts, block groups, roads, railways, and more.
- Free and updated annually.
- Essential for creating maps with Census data.
Population Estimates Program
- Provides yearly population updates between censuses.
- Includes data at the state, county, and metro level.
Economic Census
- Data on businesses, industries, and revenue.
- Updated every five years.
- Available at state, county, and metro levels.
Geographic Units Used by the Census
Census data is structured using standard geographic units. These include:
- Nation
- Regions and Divisions
- States
- Counties
- Census tracts
- Block groups
- Blocks
- Metropolitan areas
- ZCTAs (ZIP Code Tabulation Areas)
- Places (cities and towns)
- PUMAs (for ACS microdata)
Each unit has a unique ID (GEOID) for joining data to maps.
Accessing Census Bureau Data
You can get data through:
- data.census.gov – Main access point for tables and downloads.
- TIGER/Line Shapefiles – For map boundaries.
- Census API – For developers and advanced users.
- FTP sites – For bulk data.
- Census Mapper, IPUMS, Social Explorer – Simplified access from third parties.
How GIS Projects Use Census Bureau Data
Demographics
Map age, race, and household structure. Track population changes over time.
Housing
Understand home ownership, overcrowding, and housing types.
Economics
Map income, poverty, and employment patterns by area.
Infrastructure Planning
Use population and housing data to plan schools, roads, and utilities.
Social Services
Find underserved areas based on poverty or language data.
Redistricting
Use block-level population data for drawing voting districts.
Working with Census Data in GIS Platforms Like Atlas
- Join by GEOID – All data is coded with a geographic ID.
- Use TIGER files – These shapefiles match Census data perfectly.
- Filter by year – Make sure your geography and data are from the same vintage.
- Normalize values – Use percentages or rates for comparisons.
- Combine with ACS – Use ACS for recent, detailed data and Decennial Census for baseline counts.
Common Tools and Files
- .shp – Standard shapefile format for boundaries.
- .csv – Table format for most data releases.
- .geojson – Increasingly used for web maps.
- GEOID – Key column to link data and geography.
Limitations to Keep in Mind
Decennial Census is only every 10 years. Things change in between. ACS is a survey, so it has margins of error. Block-level data is detailed but harder to work with due to size. Some geographies — like ZIP codes — aren’t official boundaries and may not align perfectly.
