Iowa Counties by Population (2025)

Top 5 Most Populous Counties

Iowa flag Polk County

513,397

Iowa flag Linn County

229,036

Iowa flag Scott County

175,308

Iowa flag Johnson County

158,754

Iowa flag Black Hawk County

131,309

99 counties

County
2025 Pop. ↓
Area (mi²)
Density
Change (2020)
Polk County513,3975728984.13%
Linn County229,036717319-0.6%
Scott County175,3084583830.4%
Johnson County158,7546132593.72%
Black Hawk County131,3095662320.2%
Dallas County116,98458819916.36%
Woodbury County106,7378731220.78%
Dubuque County99,231608163-0.08%
Story County99,1845731730.54%
Pottawattamie County93,40795198-0.28%
Warren County57,0095701008.4%
Clinton County45,96469566-1%
Cerro Gordo County42,36656875-1.52%
Muscatine County41,86443796-2.96%
Marshall County40,400573710.76%
Des Moines County38,27541692-1.41%
Jasper County37,859730520.13%
Sioux County36,484768481.67%
Webster County36,15171650-2.28%
Wapello County35,336432820.03%
Marion County34,050554611.9%
Lee County32,03751862-4.46%
Boone County26,61257047-0.32%
Benton County25,904716361.39%
Plymouth County25,722863300.12%
Bremer County25,413435581.61%
Washington County22,596569400.24%
Mahaska County21,68057138-2.17%
Jones County20,802576360.72%
Buchanan County20,695571360.44%
Carroll County20,48456936-1.17%
Buena Vista County20,41357536-1.89%
Winneshiek County19,64169028-2.02%
Jackson County19,33463630-0.62%
Fayette County19,09873126-1.78%
Poweshiek County18,32358531-1.65%
Cedar County18,20057931-1.6%
Henry County18,13543442-11.31%
Dickinson County18,072381471.72%
Delaware County17,586578300.73%
Madison County16,833561301.23%
Clayton County16,79377822-1.41%
Tama County16,61372123-2.74%
Clay County16,519567291.12%
Hardin County16,16156928-3.96%
Iowa County16,14958628-3.06%
Crawford County15,78171422-4.26%
Floyd County15,28250131-2.06%
Jefferson County14,98443634-4.52%
Mills County14,829437342.99%
Page County14,69053527-3.29%
Harrison County14,650697210.56%
Hamilton County14,58157725-2.85%
Kossuth County14,25897315-3.66%
Allamakee County14,186639220.82%
Butler County14,02458024-2.16%
O'Brien County13,86657324-2.01%
Cass County13,11656423-0.05%
Lyon County12,618588215.77%
Wright County12,57858022-2.62%
Grundy County12,442502250.88%
Appanoose County12,07549724-1.73%
Shelby County11,996591202.22%
Union County11,91242428-1.81%
Cherokee County11,835577211.54%
Chickasaw County11,51850423-3.92%
Guthrie County10,804591181.81%
Hancock County10,54357118-1.96%
Mitchell County10,46646922-1.24%
Winnebago County10,43540026-2.13%
Louisa County10,30540226-4.71%
Montgomery County9,99742424-3.25%
Keokuk County9,97657917-0.28%
Calhoun County9,83957017-0.62%
Franklin County9,73358217-2.69%
Sac County9,68057517-1.21%
Clarke County9,47843122-2.66%
Humboldt County9,45843422-1.47%
Emmet County9,25939623-0.94%
Davis County9,213502181.12%
Howard County9,11047319-3.99%
Palo Alto County8,85056416-1.51%
Lucas County8,837431212.54%
Monona County8,46769412-3.15%
Greene County8,33257015-4.8%
Decatur County7,60553214-0.01%
Monroe County7,45243417-1.86%
Van Buren County7,294485151%
Worth County7,26940018-2.25%
Adair County7,25356913-3.2%
Pocahontas County6,78257712-4.01%
Wayne County6,691525132.75%
Ida County6,68943215-4.74%
Fremont County6,42451113-2.16%
Taylor County6,022532112.73%
Osceola County5,79039915-6.58%
Audubon County5,45244312-4.06%
Ringgold County4,5505359-1.92%
Adams County3,4304238-7.52%

Overview of Iowa Counties

There are 99 counties in Iowa.

The most populous county in Iowa is Polk County, home to the city of Des Moines, which has a population of 478,204 people. Since the time of the last United States census in 2010, Polk County has seen a population growth rate of 12.68%.

Following Polk County are:

The only other counties in Iowa with more than 100,000 residents are:

Johnson County had the highest growth rate of 15.17% since 2010.

Iowa Counties with the Fewest Residents

The Iowa county with the lowest population is Adams County, which has a population of just 3,648. This represents a decrease in the population of 9.4% since 2010.

Behind Adams County are:

Iowa has 25 counties with fewer than 10,000 people. Of these counties, all have experienced a declining population except two:

The greatest decline occurred in Emmet County, with a growth rate of -9.96%.

Iowa Counties with Rapid Growth

The county in Iowa with the most rapid population growth is Dallas County. Since 2010, Dallas County has been the fastest-growing county in Iowa, growing an amazing 35.11%, with the population now standing at 90,180 in 2019.

Behind Dallas County in growth are:

Emmet County has seen the highest level of population loss with a growth rate of -9.96% since 2010.

Sources

  1. US Census State Population Estimates - Most recent state estimates from the Census Bureau's Population Estimates Program
  2. US Census County Population Estimates - Most recent county estimates from the Census Bureau's Population Estimates Program
  3. American Community Survey (2009 - 2013)
  4. Census QuickFacts
  5. Historical Populations of States and Counties (1790 - 1990)