Census Bureau

How to Use This API

1. 2020 Census Population by State

https://api.census.gov/data/2020/dec/pl?get=NAME,P1_001N&for=state:*

Returns name and total population for all 50 states plus DC and Puerto Rico.

2. ACS Population by County in California

https://api.census.gov/data/2021/acs/acs1?get=NAME,B01001_001E&for=county:*&in=state:06

B01001_001E is the total population variable. state:06 is California's FIPS code.

3. Median Household Income by ZIP Code

https://api.census.gov/data/2021/acs/acs5?get=NAME,B19013_001E&for=zip%20code%20tabulation%20area:*

B19013_001E is median household income. Available in ACS 5-year estimates for finer geography.

4. Population by Age Breakdown

https://api.census.gov/data/2021/acs/acs1?get=NAME,B01001_001E,B01001_002E,B01001_003E,B01001_020E,B01001_021E,B01001_022E,B01001_023E,B01001_024E,B01001_025E&for=state:*

Age variables: B01001_003E=under 5, B01001_020E through B01001_025E=65+.

5. Find Variable Names

https://api.census.gov/data/2020/dec/pl/variables.json

https://api.census.gov/data/2021/acs/acs5/variables.json

Use the /variables.json endpoint to discover available variable codes and their descriptions.

6. Response Format

[
  ["NAME", "P1_001N", "state"],
  ["California", "39538223", "06"],
  ["Texas", "29145505", "48"],
  ["Florida", "21538187", "12"],
  ...
]

The first array is headers; subsequent arrays are data rows. Parse by index.

7. JavaScript — Get State Populations

fetch('https://api.census.gov/data/2020/dec/pl?get=NAME,P1_001N&for=state:*')
  .then(r => r.json())
  .then(data => {
    const [headers, ...rows] = data;
    rows.forEach(r => {
      console.log(`${r[0]}: ${parseInt(r[1]).toLocaleString()}`);
    });
  });

8. Python — Query by County

import requests

params = {
    'get': 'NAME,B01001_001E,B19013_001E',
    'for': 'county:*',
    'in': 'state:06'
}
resp = requests.get(
    'https://api.census.gov/data/2021/acs/acs5', params=params
)
headers, *rows = resp.json()
for row in rows:
    print(f"{row[0]}: Pop={row[1]}, MedInc=${row[2]}")

9. Python — Top 10 Most Populous States

import requests

resp = requests.get(
    'https://api.census.gov/data/2020/dec/pl',
    params={'get': 'NAME,P1_001N', 'for': 'state:*'}
)
headers, *rows = resp.json()
rows.sort(key=lambda r: int(r[1]), reverse=True)
for state in rows[:10]:
    print(f"{state[0]}: {int(state[1]):,}")