Washington County area

Population and density of Washington County

The Census Bureau estimates that 22,667 people lived in Washington County on July 1, 2025. That ranks #1,749 of 3,222 county equivalents nationally and #27 of 99 in Iowa. Since the April 1, 2020 estimates base of 22,561, the population has grown by 106 (+0.5%), compared with +1.5% for Iowa as a whole.

With 568.8 square miles of land, that is 40 people per square mile (15 per km²), placing Washington County #1,757 nationally for density and #27 in Iowa. The median county equivalent has 47 people per square mile; the Iowa median is 26. Put another way, there are about 16 acres of land per resident.

U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.

Cities and towns in Washington County

10 incorporated places lie at least partly in Washington County. Together they are home to 14,244 people (62.8%); the other 8,423 (37.2%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Washington city, with 7,261 residents in the county. Among places with at least 1,000 residents in 2020, Kalona city grew fastest since then (+6.5%).

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Washington County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.

Metropolitan area

Washington County is an outlying county of the Iowa City, IA Metropolitan Statistical Area. Its 2 county equivalents have 182,711 residents on 1,181.8 square miles of land; Washington County accounts for 48.1% of the land and 12.4% of the residents. By combined land it ranks #262 of 393 metropolitan areas, and #252 by population. It belongs to the Cedar Rapids-Iowa City, IA Combined Statistical Area.

ZIP codes

13 ZIP Code Tabulation Areas have land in Washington County; 7 of them have most of their land inside the county, and the others mainly cover neighboring areas.

52201522475224852327523535235652359525405258552621526415265452738

ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.

Counties bordering Washington County

Washington County shares a land border with 6 county equivalents. It has more land than 3 of them. The largest neighbor is Johnson County (613 mi²) and the smallest is Louisa County (401.8 mi²). Together with its neighbors, Washington County forms a block of 3,619 mi² of land, of which it holds 15.7%.

How big is Washington County compared with U.S. states?

Washington County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 1.8 times as much. Iowa’s county land could hold about 98 areas the size of Washington County.

Another way to picture it: the same land area would fill a square about 23.9 miles (38.4 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.

State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.

What stands out about Washington County?

Washington County has more land than 1,429 of the other 3,221 county equivalents in the dataset.

A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.

Does including water change its rank?

Using land plus water places Washington County at #1,922 nationally by total area, 129 places farther from the top than its land rank. Other county equivalents gain more area when their water measurements are included.

Its water share is 0.4%, compared with a national county-equivalent median of 1.2% — 0.8 percentage points lower. This describes the statistical geography’s land/water mix, not flood exposure or developable land.

Closest positions in the national land ranking

These entries sit immediately beside Washington County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.