US Census Bureau Data API
Provides programmatic access to US Census Bureau datasets including the American Community Survey, Decennial Census, Economic Census, and population estimates for geographic units from national down to census tract level.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Public aggregate government data with no PII. API key in query param. No scopes or restrictions needed for public data, but key management still matters.
⚡ Reliability
Best When
You need authoritative US demographic, economic, or geographic aggregate data at any geographic resolution from national to census tract level.
Avoid When
You need current-year estimates, individual records, or data updated more frequently than annual survey cycles.
Use Cases
- • Query ACS 5-year estimates for median household income and poverty rates by county to enrich a market analysis or site selection agent
- • Retrieve population estimates by age group and race for a set of ZIP codes to support demographic targeting workflows
- • Fetch business establishment counts and employment figures by NAICS industry code for a metropolitan area for economic research agents
- • Pull housing unit counts, vacancy rates, and owner/renter ratios for census tracts to support real estate intelligence pipelines
- • Retrieve decennial census data for historical population comparison across decades to power long-term trend analysis
Not For
- • Individual-level or household-level microdata — all responses are aggregate statistics
- • Real-time population data — census data lags by 1-5 years depending on the dataset
- • Non-US geographic areas or international demographic comparisons
Interface
Authentication
API key is optional but strongly recommended — unauthenticated requests are limited to 500/day. Key passed as query param `key=YOUR_KEY`. Registration is free and instant.
Pricing
Completely free public service. API key registration is instant via web form.
Agent Metadata
Known Gotchas
- ⚠ Variable codes (e.g., `B19013_001E`) are dataset and year-specific — the same variable name may not exist across ACS vintages, causing silent empty responses
- ⚠ Geographic hierarchy encoding requires knowing FIPS codes for state, county, tract, etc. — plain names are not accepted in `for` and `in` parameters
- ⚠ The query parameter syntax (`get=VAR1,VAR2&for=county:*&in=state:06`) is unique and unlike standard REST conventions
- ⚠ Response format is a JSON array of arrays (not an array of objects) — the first row is the header row, requiring custom parsing logic
- ⚠ Some dataset endpoints return HTTP 200 with an error string in the body rather than a non-200 status code
Alternatives
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Continuous monitoring
Scores are editorial opinions as of 2026-03-07.