Washington County area

Population and density of Washington County

The Census Bureau estimates that 139,238 people lived in Washington County on July 1, 2025. That ranks #488 of 3,222 county equivalents nationally and #11 of 72 in Wisconsin. Since the April 1, 2020 estimates base of 136,770, the population has grown by 2,468 (+1.8%), compared with +1.3% for Wisconsin as a whole.

With 430.6 square miles of land, that is 323 people per square mile (125 per km²), placing Washington County #483 nationally for density and #9 in Wisconsin. The median county equivalent has 47 people per square mile; the Wisconsin median is 51. Put another way, there are about 2 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

Washington County is divided into 21 cities and towns. In Wisconsin, county subdivisions are local governments, and together they cover all of the county’s land and residents.

The most populous is West Bend city, with 32,268 residents (23.2% of the county). The largest by land is Farmington town, at 36.5 mi², or 8.5% of the county’s land. Among those with at least 1,000 residents in 2020, Slinger village grew fastest since then (+8.2%).

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each subdivision inside Washington County. Land: 2026 Census Gazetteer. How communities are listed.

Metropolitan area

Washington County is an outlying county of the Milwaukee-Waukesha, WI Metropolitan Statistical Area. Its 4 county equivalents have 1,575,010 residents on 1,454.8 square miles of land; Washington County accounts for 29.6% of the land and 8.8% of the residents. By combined land it ranks #225 of 393 metropolitan areas, and #42 by population. It belongs to the Milwaukee-Racine-Waukesha, WI Combined Statistical Area.

ZIP codes

18 ZIP Code Tabulation Areas have land in Washington County; 11 of them have most of their land inside the county, and the others mainly cover neighboring areas.

530025301053012530175302153022530275302953033530375304053066530755307653086530905309153095

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 5 county equivalents. It has more land than 1 of them. The largest neighbor is Dodge County (875.7 mi²) and the smallest is Ozaukee County (233 mi²). Together with its neighbors, Washington County forms a block of 3,320.2 mi² of land, of which it holds 13%.

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 2.4 times as much. Wisconsin’s county land could hold about 126 areas the size of Washington County.

Another way to picture it: the same land area would fill a square about 20.8 miles (33.4 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 859 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 #2,414 nationally by total area, 51 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 1.2%, compared with a national county-equivalent median of 1.2%. The two percentages are within 0.1 percentage points of each other. 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.