Lancaster County
Nebraska · County seat: Lincoln · Active county or equivalent
FIPS code 31109 is Lancaster County, Nebraska. With a population of 322,063 (2022 ACS estimate), it ranks #2 in Nebraska and #220 nationally. Lancaster County is part of the Lincoln, NE. The state FIPS code for Nebraska is 31. This code is used in Census Bureau, BLS, EPA, HUD, and USDA federal datasets to identify this county.
County FIPS
31109
Population
322,063
2022 ACS · #220 nationally
Density
384.5/mi²
people per sq mile
Land Area
838
sq miles
Urban/Rural
Metro — 250K–1M population
RUCC 2
How This FIPS Code Works
The 5-digit FIPS code 31109 is formed by combining the 2-digit state identifier 31 (Nebraska) with the 3-digit county identifier 109. Together they uniquely identify Lancaster County in every US federal dataset. No two counties share the same 5-digit FIPS code.
Census ACS Data for FIPS 31109
From the 2022 ACS 5-year estimates — the same values you'd retrieve by querying the Census API with county FIPS 31109.
Median Household Income
$70,387
ACS B19013_001E
Poverty Rate
11.8%
ACS B17001 (below poverty level)
Median Age
34.1
ACS B01002_001E
Metropolitan Area
Adjacent Counties (8)
Counties that share a border with Lancaster County. Useful for regional analysis — these are the geographies you'd typically include when studying labor markets, commuting zones, or environmental spillovers around FIPS 31109.
Federal Datasets Using Code 31109
FIPS code 31109 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 31109 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:109",
"in": "state:31",
"key": "YOUR_CENSUS_API_KEY",
}
r = requests.get(url, params=params)
data = r.json() # [[header...], [Lancaster County, Nebraska, income, pop, ...]-- 5-digit combined FIPS (state + county)
SELECT * FROM your_table WHERE county_fips = '31109';
-- Some datasets store state and county separately
SELECT * FROM your_table
WHERE state_fips = '31'
AND county_fips = '109';
-- ⚠ Never cast to integer — leading zeros are lost:
-- county_fips = 31109 is WRONG for this countylibrary(tidycensus)
get_acs(
geography = "county",
variables = c(income = "B19013_001E", pop = "B01003_001E"),
state = "31",
county = "109",
year = 2022
)ZIP Codes in Lancaster 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 Lancaster County. Why FIPS ≠ ZIP →
| ZIP Code | % in county |
|---|---|
| 68588 | 100.0% |
| 68507 | 100.0% |
| 68508 | 100.0% |
| 68510 | 100.0% |
| 68512 | 100.0% |
| 68514 | 100.0% |
| 68516 | 100.0% |
| 68517 | 100.0% |
| 68520 | 100.0% |
| 68521 | 100.0% |
| 68522 | 100.0% |
| 68523 | 100.0% |
| 68524 | 100.0% |
| 68526 | 100.0% |
| 68531 | 100.0% |
| 68532 | 100.0% |
| 68336 | 100.0% |
| 68372 | 100.0% |
| 68402 | 100.0% |
| 68404 | 100.0% |
| 68419 | 100.0% |
| 68430 | 100.0% |
| 68438 | 100.0% |
| 68461 | 100.0% |
| 68502 | 100.0% |
| 68503 | 100.0% |
| 68504 | 100.0% |
| 68505 | 100.0% |
| 68506 | 100.0% |
| 68528 | 99.0% |
Showing top 30 of 44 ZIP codes by residential address share.