Mahaska County area

Population and density of Mahaska County

The Census Bureau estimates that 21,880 people lived in Mahaska County on July 1, 2025. That ranks #1,780 of 3,222 county equivalents nationally and #28 of 99 in Iowa. Since the April 1, 2020 estimates base of 22,182, the population has declined by 302 (−1.4%), compared with +1.5% for Iowa as a whole.

With 570.9 square miles of land, that is 38 people per square mile (15 per km²), placing Mahaska County #1,787 nationally for density and #28 in Iowa. The median county equivalent has 47 people per square mile; the Iowa median is 26. Put another way, there are about 17 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 Mahaska County

11 incorporated places lie at least partly in Mahaska County. Together they are home to 15,105 people (69%); the other 6,775 (31%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Oskaloosa city, with 11,493 residents in the county. By land, Pella city is the largest at 9.343 mi² across all its counties.

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

Metropolitan area

Mahaska County is a central county of the Oskaloosa, IA Micropolitan Statistical Area. Mahaska County is the area’s only county equivalent, so the micro area has the same 570.9 square miles of land. By combined land it ranks #377 of 542 micropolitan areas, and #499 by population. It belongs to the Des Moines-West Des Moines-Ames, IA Combined Statistical Area.

ZIP codes

20 ZIP Code Tabulation Areas have land in Mahaska County; 9 of them have most of their land inside the county, and the others mainly cover neighboring areas.

5002750044501045014350153501715020750219502515025650268525015253452543525505255352561525775258652595

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 Mahaska County

Mahaska County shares a land border with 6 county equivalents. It has more land than 3 of them. The largest neighbor is Jasper County (730.4 mi²) and the smallest is Wapello County (431.8 mi²). Together with its neighbors, Mahaska County forms a block of 3,885.4 mi² of land, of which it holds 14.7%.

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

Mahaska 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 Mahaska County.

Another way to picture it: the same land area would fill a square about 23.9 miles (38.5 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 Mahaska County?

Mahaska County has more land than 1,457 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 Mahaska County at #1,896 nationally by total area, 131 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% — 0.7 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 Mahaska 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.