Marshall County
Indiana · County seat: Plymouth · Active county or equivalent
FIPS code 18099 is Marshall County, Indiana. With a population of 46,208 (2022 ACS estimate), it ranks #32 in Indiana and #1060 nationally. Marshall County is part of the Plymouth, IN. The state FIPS code for Indiana is 18. This code is used in Census Bureau, BLS, EPA, HUD, and USDA federal datasets to identify this county.
County FIPS
18099
Population
46,208
2022 ACS · #1060 nationally
Density
104.2/mi²
people per sq mile
Land Area
444
sq miles
Urban/Rural
Nonmetro — urban 2.5K–19.9K, adjacent to metro
RUCC 6
How This FIPS Code Works
The 5-digit FIPS code 18099 is formed by combining the 2-digit state identifier 18 (Indiana) with the 3-digit county identifier 099. 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 18099
From the 2022 ACS 5-year estimates — the same values you'd retrieve by querying the Census API with county FIPS 18099.
Median Household Income
$66,016
ACS B19013_001E
Poverty Rate
10.8%
ACS B17001 (below poverty level)
Median Age
39.9
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 18099.
Federal Datasets Using Code 18099
FIPS code 18099 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 18099 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:099",
"in": "state:18",
"key": "YOUR_CENSUS_API_KEY",
}
r = requests.get(url, params=params)
data = r.json() # [[header...], [Marshall County, Indiana, income, pop, ...]-- 5-digit combined FIPS (state + county)
SELECT * FROM your_table WHERE county_fips = '18099';
-- Some datasets store state and county separately
SELECT * FROM your_table
WHERE state_fips = '18'
AND county_fips = '099';
-- ⚠ Never cast to integer — leading zeros are lost:
-- county_fips = 18099 is WRONG for this countylibrary(tidycensus)
get_acs(
geography = "county",
variables = c(income = "B19013_001E", pop = "B01003_001E"),
state = "18",
county = "099",
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 |
|---|---|
| 46537 | 100.0% |
| 46513 | 100.0% |
| 46572 | 100.0% |
| 46563 | 98.6% |
| 46570 | 97.7% |
| 46501 | 96.8% |
| 46504 | 95.8% |
| 46511 | 64.7% |
| 46506 | 61.5% |
| 46574 | 25.0% |
| 46536 | 8.6% |
| 46550 | 6.5% |
| 46539 | 5.8% |
| 46524 | 1.4% |
| 46531 | 1.1% |