ZIP Codes of Clay County, IA

Population & People
Population & People
Total Population
15,999
Household Income
Household Income
Median Income
$79,930
Housing
Housing
Total Housing Units
7,921
Business & Economy
Business & Economy
Total Businesses
557
Employment
Employment
Employment Rate
64.37%
Education
Education
Bachelor's Degree+
27.56%
Source: U.S. Census ACS 2024 5-Year Estimates · rolled up across the 9 ZIPs in this county.
Data Last Updated: July 1, 2026
ZIP Codes:9 ZIP Codes (7 Standard, 2 PO Box, 0 Unique) [See All]
Area Code:712
Timezone:Central (GMT -06:00)
Local Time:11:53:09 PM
Population:15,999 [See All]
FIPS:19041
CBSA:Spencer, IA
Land Area:502 sq mi
Water Area:2 sq mi
Coordinates:43.0868, -95.1599
Quick Link:
https://www.zip-codes.com/county/ia-clay.asp
Need Clay data in your app? Look up ZIP, county, and city data with a single API call.
Try Free
Iowa's #46 most populous county
15,999 residents across 9 ZIPs — #46 of 99 Iowa counties.

Standout ZIPs in this County


Most Populous
Spencer · 12,638 people
79.0% of county total
Highest Income
Dickens · $110,833 median
1.4× county average
Largest Land Area
Spencer · 164.4 sq mi
Spans the most ground
Fastest Growth
Spencer · -2.1% (10-yr)
12,905 → 12,638 residents
Most Educated
Spencer · 29.0% bachelor's+
2,566 of 8,838 adults 25+

Things worth knowing about Clay County


15,999 residents live across 9 ZIPs covering 502 sq mi, served by 9 distinct USPS-recognized cities.

Population moved from 16,353 to 15,924 from 2014 to 2024 — a -2.6% change. 1 ZIPs gained residents, 7 lost.

The county's wealthiest ZIP 51333 (Dickens, $110,833 median) and poorest ZIP 51338 (Everly, $57,500) are 16.7 miles apart — a 1.9× income gap across local geography.

Median home values vary 2.0× across this county — from $98,800 in 51343 (Greenville) to $195,600 in 51333 (Dickens).

Density varies 20× across the county — from 4 people/sq mi in 51366 (Webb) to 77 in 51301 (Spencer).

Educational attainment ranges from 5.9% bachelor's+ in 51343 (Greenville) to 30.5% in 51047 (Peterson) — the breadth of educational profiles across the area.

Within Iowa, this is the #46 most populous of 99 counties and ranks #26 for median household income .

Weighted by population, the typical household earns about $66,578 across the county — reflecting what a typical resident sees, not a simple ZIP average.

27.6% of adults age 25+ hold a bachelor's degree or higher (3,069 of 11,136 reporting).

7 Standard delivery, 2 PO Box only, 0 single-entity Unique ZIPs serve this county.

Stories about Clay County


Big & sparse

A frontier county — vast land area with only a few residents per square mile. Daily life looks very different here than in the country's denser counties.

Total area
502
square miles
Avg density
31.9
people per sq mi
Population
15,999
across 9 ZIPs
Spencer
164.4 sq mi
12,638 residents
Peterson
75.3 sq mi
693 residents
Dickens
70.9 sq mi
374 residents

Single-ZIP anchor

One ZIP holds the majority of this county's population — a sign of a county built around a single city or town.

Spencer

All ZIP Codes in Clay County


ZIPCityTypePopulationMedian IncomeArea (sq mi)10-yr Growth
51301SpencerStandard12,638$63,402164.4-2.1%
51357RoyalStandard910$68,33336.614.2%
51338EverlyStandard852$57,50066.8-6.7%
51047PetersonStandard693$101,00075.3-0.7%
51333DickensStandard374$110,83370.9-5.3%
51366WebbStandard245$87,50063.0-31.0%
51343GreenvilleStandard172$60,62524.3-22.5%
51340FostoriaPO Box75$90,2500.3
51341Gillett GrovePO Box400.2-41.2%

Adjacent & Nearby Counties