FIPS code 17123 is Marshall County, Illinois. With a population of 11,740 (2022 ACS estimate), it ranks #85 in Illinois and #2362 nationally. Marshall County is part of the Peoria, IL. The state FIPS code for Illinois is 17. This code is used in Census Bureau, BLS, EPA, HUD, and USDA federal datasets to identify this county.
County FIPS
17123
Population
11,740
2022 ACS · #2362 nationally
Density
30.4/mi²
people per sq mile
Land Area
387
sq miles
Urban/Rural
Metro — 250K–1M population
RUCC 2
How This FIPS Code Works
The 5-digit FIPS code 17123 is formed by combining the 2-digit state identifier 17 (Illinois) with the 3-digit county identifier 123. Together they uniquely identify Marshall County in every US federal dataset. No two counties share the same 5-digit FIPS code.
Census ACS Data for FIPS 17123
From the 2022 ACS 5-year estimates — the same values you'd retrieve by querying the Census API with county FIPS 17123.
Median Household Income
$64,940
ACS B19013_001E
Poverty Rate
12.3%
ACS B17001 (below poverty level)
Median Age
46.2
ACS B01002_001E
Metropolitan Area
Adjacent Counties (6)
Counties that share a border with Marshall County. Useful for regional analysis — these are the geographies you'd typically include when studying labor markets, commuting zones, or environmental spillovers around FIPS 17123.
Federal Datasets Using Code 17123
FIPS code 17123 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 17123 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:123",
"in": "state:17",
"key": "YOUR_CENSUS_API_KEY",
}
r = requests.get(url, params=params)
data = r.json() # [[header...], [Marshall County, Illinois, income, pop, ...]-- 5-digit combined FIPS (state + county)
SELECT * FROM your_table WHERE county_fips = '17123';
-- Some datasets store state and county separately
SELECT * FROM your_table
WHERE state_fips = '17'
AND county_fips = '123';
-- ⚠ Never cast to integer — leading zeros are lost:
-- county_fips = 17123 is WRONG for this countylibrary(tidycensus)
get_acs(
geography = "county",
variables = c(income = "B19013_001E", pop = "B01003_001E"),
state = "17",
county = "123",
year = 2022
)ZIP Codes in Marshall 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 Marshall County. Why FIPS ≠ ZIP →
| ZIP Code | % in county |
|---|---|
| 61541 | 100.0% |
| 61369 | 100.0% |
| 61375 | 100.0% |
| 61424 | 100.0% |
| 61540 | 100.0% |
| 61565 | 98.9% |
| 61537 | 94.7% |
| 61479 | 51.1% |
| 61377 | 49.8% |
| 61358 | 46.4% |
| 61570 | 44.1% |
| 61336 | 44.1% |
| 61491 | 10.8% |
| 61421 | 9.0% |
| 61526 | 8.2% |
| 61760 | 7.7% |
| 61523 | 6.4% |
| 61560 | 4.2% |
| 61321 | 3.2% |