TIGER/Line shapefiles are the geographic building blocks of U.S. Census data. They are free files that contain the shapes and boundaries for things like counties, census tracts, roads, railroads, rivers, and ZIP code areas.
If you are doing any kind of mapping with U.S. Census data, you’ll need TIGER/Line files. They are built and maintained by the U.S. Census Bureau and updated every year.
What Is TIGER/Line?
TIGER stands for “Topologically Integrated Geographic Encoding and Referencing.” It’s a system that represents geographic features for use in maps and spatial analysis. TIGER/Line shapefiles are simply versions of this data that can be used in GIS software. These files help turn tables of data (like population or income) into maps. They define the shape and size of every geographic unit used in Census data.
What Does It Include?
TIGER/Line shapefiles cover a wide range of features:
Boundaries
- States
- Counties
- Census tracts
- Block groups
- Blocks
- Places (cities/towns)
- School districts
- ZIP Code Tabulation Areas (ZCTAs)
- Voting districts
Features
- Roads (with classifications)
- Railroads
- Rivers and water bodies
- Legal and administrative boundaries
- Landmarks
- Military bases
Each file set includes a shapefile and a data table with unique identifiers like GEOID.
Where to Get TIGER/Line Files
You can download TIGER/Line shapefiles from the Census Bureau’s website:
Files are available for national, state, and county levels.
You can select specific years, geographies, and formats.
How to Use in GIS Platforms Like Atlas
TIGER/Line files are standard shapefiles (.shp) and work with most GIS platforms.
Here’s how to use them:
- Download the correct geography (e.g., census tracts for your state)
- Load the shapefile into your GIS tool (Atlas, QGIS, ArcGIS, etc.)
- Join your data using the GEOID field (e.g., from ACS or Decennial Census)
- Style or filter as needed (e.g., color tracts by median income)
You can also combine layers—for example, overlay school district boundaries with roads and population.
Why TIGER/Line Matters
TIGER/Line gives shape to the data. Without it, Census data would just be tables of numbers.
With it, you can:
- Map where people live
- Analyze service areas
- Plan public infrastructure
- Track environmental impacts
- Understand urban growth
It provides the geographic structure behind nearly every U.S. demographic map.
Common Use Cases
Population Mapping
Use tract or block group boundaries to show population density, diversity, or age distribution.
Economic and Housing Maps
Map income, housing costs, or overcrowding using census tracts and ZCTAs.
Service Planning
Use school district or voting precinct files to analyze service coverage.
Transportation Maps
Use road and rail shapefiles for routing, accessibility, or planning.
Emergency and Disaster Maps
Overlay flood zones or fire risk areas with populated block groups.
Key Attributes in TIGER/Line Files
- GEOID – The geographic identifier, used to link data.
- NAME – The name of the geography (e.g., county name).
- LSAD – Legal status (e.g., city, town).
- INTPTLAT/INTPTLON – Latitude and longitude of the shape center.
- MTFCC – Feature classification code (for roads, railways, etc.)
These fields help control how you display and filter the data in maps.
Tips for Working with TIGER/Line
- Check the year – Use the same vintage for geography and data.
- Use GEOID for joining – Always match data using full GEOIDs.
- Simplify for web maps – Large files can slow down browser-based platforms.
- Clip to area of interest – Focus on a city or county for better performance.
- Combine with ACS or Census – For richer maps with real-world meaning.
Limitations to Know
TIGER/Line files aren’t perfect. Roads and boundaries are simplified and not always aligned with local data. ZCTAs don’t always match postal ZIP codes. Water bodies may be outdated in some areas. Still, they’re the most consistent and complete free geographic files for U.S. mapping.
