Waukesha County
Wisconsin · County seat: Waukesha · Active county or equivalent
FIPS code 55133 is Waukesha County, Wisconsin. With a population of 407,290 (2022 ACS estimate), it ranks #3 in Wisconsin and #172 nationally. Waukesha County is part of the Milwaukee-Waukesha, WI. The state FIPS code for Wisconsin is 55. This code is used in Census Bureau, BLS, EPA, HUD, and USDA federal datasets to identify this county.
County FIPS
55133
Population
407,290
2022 ACS · #172 nationally
Density
741.1/mi²
people per sq mile
Land Area
550
sq miles
Urban/Rural
Metro — 1M+ population
RUCC 1
How This FIPS Code Works
The 5-digit FIPS code 55133 is formed by combining the 2-digit state identifier 55 (Wisconsin) with the 3-digit county identifier 133. Together they uniquely identify Waukesha County in every US federal dataset. No two counties share the same 5-digit FIPS code.
Census ACS Data for FIPS 55133
From the 2022 ACS 5-year estimates — the same values you'd retrieve by querying the Census API with county FIPS 55133.
Median Household Income
$101,639
ACS B19013_001E
Poverty Rate
5.0%
ACS B17001 (below poverty level)
Median Age
43.3
ACS B01002_001E
Metropolitan Area
Adjacent Counties (7)
Counties that share a border with Waukesha County. Useful for regional analysis — these are the geographies you'd typically include when studying labor markets, commuting zones, or environmental spillovers around FIPS 55133.
Federal Datasets Using Code 55133
FIPS code 55133 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 55133 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:133",
"in": "state:55",
"key": "YOUR_CENSUS_API_KEY",
}
r = requests.get(url, params=params)
data = r.json() # [[header...], [Waukesha County, Wisconsin, income, pop, ...]-- 5-digit combined FIPS (state + county)
SELECT * FROM your_table WHERE county_fips = '55133';
-- Some datasets store state and county separately
SELECT * FROM your_table
WHERE state_fips = '55'
AND county_fips = '133';
-- ⚠ Never cast to integer — leading zeros are lost:
-- county_fips = 55133 is WRONG for this countylibrary(tidycensus)
get_acs(
geography = "county",
variables = c(income = "B19013_001E", pop = "B01003_001E"),
state = "55",
county = "133",
year = 2022
)ZIP Codes in Waukesha 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 Waukesha County. Why FIPS ≠ ZIP →
| ZIP Code | % in county |
|---|---|
| 53151 | 100.0% |
| 53007 | 100.0% |
| 53189 | 100.0% |
| 53018 | 100.0% |
| 53146 | 100.0% |
| 53183 | 100.0% |
| 53153 | 100.0% |
| 53188 | 100.0% |
| 53045 | 100.0% |
| 53046 | 100.0% |
| 53051 | 100.0% |
| 53058 | 100.0% |
| 53186 | 100.0% |
| 53069 | 100.0% |
| 53072 | 100.0% |
| 53089 | 100.0% |
| 53103 | 100.0% |
| 53005 | 100.0% |
| 53122 | 100.0% |
| 53127 | 100.0% |
| 53029 | 96.8% |
| 53150 | 94.7% |
| 53119 | 88.8% |
| 53118 | 87.1% |
| 53149 | 84.4% |
| 53066 | 68.9% |
| 53017 | 12.5% |
| 53036 | 4.8% |
| 53225 | 1.5% |
| 53185 | 0.9% |
Showing top 30 of 31 ZIP codes by residential address share.