San Mateo County
California · County seat: Redwood City · Active county or equivalent
FIPS code 06081 is San Mateo County, California. With a population of 754,250 (2022 ACS estimate), it ranks #15 in California and #86 nationally. San Mateo County is part of the San Francisco-Oakland-Fremont, CA. The state FIPS code for California is 06. This code is used in Census Bureau, BLS, EPA, HUD, and USDA federal datasets to identify this county.
County FIPS
06081
Population
754,250
2022 ACS · #86 nationally
Density
1,682.1/mi²
people per sq mile
Land Area
448
sq miles
Urban/Rural
Metro — 1M+ population
RUCC 1
How This FIPS Code Works
The 5-digit FIPS code 06081 is formed by combining the 2-digit state identifier 06 (California) with the 3-digit county identifier 081. Together they uniquely identify San Mateo County in every US federal dataset. No two counties share the same 5-digit FIPS code.
Census ACS Data for FIPS 06081
From the 2022 ACS 5-year estimates — the same values you'd retrieve by querying the Census API with county FIPS 06081.
Median Household Income
$149,907
ACS B19013_001E
Poverty Rate
6.4%
ACS B17001 (below poverty level)
Median Age
40.3
ACS B01002_001E
Metropolitan Area
Adjacent Counties (4)
Counties that share a border with San Mateo County. Useful for regional analysis — these are the geographies you'd typically include when studying labor markets, commuting zones, or environmental spillovers around FIPS 06081.
Federal Datasets Using Code 06081
FIPS code 06081 appears as the county identifier in the following federal datasets. Analysts joining data across these sources use this code as the common geographic key.
Using FIPS Code 06081 in Code
Common patterns for querying federal datasets by this county's FIPS code. The leading zeros are significant — always treat FIPS codes as strings, not integers.
import requests
url = "https://api.census.gov/data/2022/acs/acs5"
params = {
"get": "NAME,B19013_001E,B01003_001E",
"for": "county:081",
"in": "state:06",
"key": "YOUR_CENSUS_API_KEY",
}
r = requests.get(url, params=params)
data = r.json() # [[header...], [San Mateo County, California, income, pop, ...]-- 5-digit combined FIPS (state + county)
SELECT * FROM your_table WHERE county_fips = '06081';
-- Some datasets store state and county separately
SELECT * FROM your_table
WHERE state_fips = '06'
AND county_fips = '081';
-- ⚠ Never cast to integer — leading zeros are lost:
-- county_fips = 6081 is WRONG for this countylibrary(tidycensus)
get_acs(
geography = "county",
variables = c(income = "B19013_001E", pop = "B01003_001E"),
state = "06",
county = "081",
year = 2022
)ZIP Codes in San Mateo County
ZIP codes do not align perfectly with county boundaries — a single ZIP code can span multiple counties, and a county can contain parts of many ZIP codes. The ratios below (from the Census 2020 ZCTA relationship file) show the land area share of each ZCTA that falls within San Mateo County. Why FIPS ≠ ZIP →
| ZIP Code | % in county |
|---|---|
| 94404 | 100.0% |
| 94005 | 100.0% |
| 94010 | 100.0% |
| 94014 | 100.0% |
| 94015 | 100.0% |
| 94018 | 100.0% |
| 94019 | 100.0% |
| 94020 | 100.0% |
| 94021 | 100.0% |
| 94025 | 100.0% |
| 94027 | 100.0% |
| 94403 | 100.0% |
| 94002 | 100.0% |
| 94030 | 100.0% |
| 94037 | 100.0% |
| 94038 | 100.0% |
| 94044 | 100.0% |
| 94060 | 100.0% |
| 94061 | 100.0% |
| 94062 | 100.0% |
| 94063 | 100.0% |
| 94065 | 100.0% |
| 94066 | 100.0% |
| 94070 | 100.0% |
| 94074 | 100.0% |
| 94080 | 100.0% |
| 94128 | 100.0% |
| 94401 | 100.0% |
| 94402 | 100.0% |
| 94028 | 81.1% |
Showing top 30 of 31 ZIP codes by residential address share.