ZIP Codes of Washington County, IA

Population & People
Population & People
Total Population
24,763
Household Income
Household Income
Median Income
$75,303
Housing
Housing
Total Housing Units
10,274
Business & Economy
Business & Economy
Total Businesses
734
Employment
Employment
Employment Rate
65.43%
Education
Education
Bachelor's Degree+
26.24%
Source: U.S. Census ACS 2024 5-Year Estimates · rolled up across the 8 ZIPs in this county.
Data Last Updated: June 1, 2026
ZIP Codes:8 ZIP Codes (8 Standard, 0 PO Box, 0 Unique) [See All]
Area Code:319
Timezone:Central (GMT -06:00)
Local Time:2:11:55 PM
Population:24,763 [See All]
FIPS:19183
CBSA:Iowa City, IA
Land Area:633 sq mi
Water Area:2 sq mi
Coordinates:41.3578, -91.6934
Quick Link:
https://www.zip-codes.com/county/ia-washington.asp
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Iowa's #25 most populous county
24,763 residents across 8 ZIPs — #25 of 99 Iowa counties.

Standout ZIPs in this County


Most Populous
Washington · 9,241 people
37.3% of county total
Highest Income
Ainsworth · $93,750 median
1.2× county average
Largest Land Area
Washington · 156.9 sq mi
Spans the most ground
Fastest Growth
Riverside · 10.7% (10-yr)
3,430 → 3,796 residents
Most Educated
Kalona · 35.1% bachelor's+
1,320 of 3,762 adults 25+

Things worth knowing about Washington County


24,763 residents live across 8 ZIPs covering 633 sq mi, served by 8 distinct USPS-recognized cities.

Population moved from 24,625 to 24,763 from 2014 to 2024 — a +0.6% change. 4 ZIPs gained residents, 4 lost.

The county's wealthiest ZIP 52201 (Ainsworth, $93,750 median) and poorest ZIP 52540 (Brighton, $55,000) are 19.2 miles apart — a 1.7× income gap across local geography.

Median home values vary 3.0× across this county — from $98,200 in 52621 (Crawfordsville) to $298,900 in 52247 (Kalona).

Density varies across the county — from 11 people/sq mi in 52540 (Brighton) to 76 in 52247 (Kalona).

Educational attainment ranges from 5.2% bachelor's+ in 52201 (Ainsworth) to 35.1% in 52247 (Kalona) — the breadth of educational profiles across the area.

Within Iowa, this is the #25 most populous of 99 counties and ranks #40 for median household income .

Weighted by population, the typical household earns about $74,594 across the county — reflecting what a typical resident sees, not a simple ZIP average.

26.2% of adults age 25+ hold a bachelor's degree or higher (4,363 of 16,628 reporting).

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

Stories about Washington 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
633
square miles
Avg density
39.1
people per sq mi
Population
24,763
across 8 ZIPs
Washington
156.9 sq mi
9,241 residents
Brighton
98.9 sq mi
1,088 residents
Wellman
96.3 sq mi
2,664 residents

All ZIP Codes in Washington County


ZIPCityTypePopulationMedian IncomeArea (sq mi)10-yr Growth
52353WashingtonStandard9,241$63,047156.92.5%
52247KalonaStandard5,914$91,45078.05.3%
52327RiversideStandard3,796$86,94281.410.7%
52356WellmanStandard2,664$57,32196.3-7.4%
52201AinsworthStandard1,148$93,75064.1-13.6%
52540BrightonStandard1,088$55,00098.9-20.9%
52621CrawfordsvilleStandard604$87,18843.8-17.0%
52359West ChesterStandard308$67,72713.322.2%

Adjacent & Nearby Counties