Polk County

History

Polk County was formed on January 13, 1846 and organized on March 1, 1846., the legislative body of the Iowa Territory authorized the creation of twelve counties in the Territory, with general descriptions of their boundaries. On January 17 they further enacted a resolution setting the effective date of the county government for Jasper and Polk Counties as March 1, 1846. Polk County's name referred to United States President James K. Polk, who served from 1845 to 1849.

The first courthouse, a two-story structure, was built in Des Moines in 1846. Rapid settlement and commercial growth in the county soon rendered this building insufficient, so construction of a larger building was initiated in 1858. Due to construction delays and the onset of the Civil War, the structure was not completed until 1866. The present courthouse was erected in 1906, and in 1962 it was extensively renovated and enlarged.

Geography

According to the United States Census Bureau, the county has a total area of 591.888 square miles (1,532.98 km2), of which 572.720 square miles (1,483.34 km2) is land and 19.168 square miles (49.64 km2) (3.24%) is water. It is the 41st-largest county in Iowa by total area The county is bisected by the Des Moines River.

Major highways

Interstate 35

Interstate 80

Interstate 235

U.S. Highway 6

U.S. Highway 65

U.S Route 69

Iowa Highway 5

Iowa Highway 17

Iowa Highway 28

Iowa Highway 141

Iowa Highway 160

Iowa Highway 163

Iowa Highway 210

Iowa Highway 415

Transit

Des Moines Area Regional Transit

Burlington Trailways

Jefferson Lines

Des Moines Bus Station

Demographics

As of the second quarter of 2025, the median home value in Polk County was $293,337.

As of the 2024 American Community Survey, there are 211,294 estimated households in Polk County with an average of 2.40 persons per household. The county has a median household income of $82,405. Approximately 9.9% of the county's population lives at or below the poverty line. Polk County has an estimated 69.4% employment rate, with 41.5% of the population holding a bachelor's degree or higher and 92.4% holding a high school diploma. There were 224,898 housing units at an average density of 392.68 per square mile (151.6/km2).

The top five reported languages (people were allowed to report up to two languages, thus the figures will generally add to more than 100%) were English (85.0%), Spanish (6.6%), Indo-European (3.2%), Asian and Pacific Islander (3.4%), and Other (1.9%).

The median age in the county was 36.2 years.

2024 estimate

As of the 2024 estimate, there were 516,185 people, 211,294 households, and _ families residing in the county. The population density was 901.29 inhabitants per square mile (348.0/km2). There were 224,898 housing units at an average density of 392.68 per square mile (151.6/km2). The racial makeup of the county was 82.8% White (72.7% NH White), 8.2% African American, 0.6% Native American, 5.5% Asian, 0.1% Pacific Islander, _% from some other races and 2.8% from two or more races. Hispanic or Latino people of any race were 11.2% of the population.

2020 census

As of the 2020 census, there were 492,401 people, 196,891 households, and 121,993 families residing in the county. The population density was 859.76 inhabitants per square mile (332.0/km2). There were 210,184 housing units at an average density of 366.99 per square mile (141.7/km2). The racial makeup of the county was 75.93% White, 7.23% African American, 0.46% Native American, 4.98% Asian, 0.06% Pacific Islander, 3.88% from some other races and 7.45% from two or more races. Hispanic or Latino people of any race were 9.76% of the population.

The median age was 36.0 years. 24.5% of residents were under the age of 18 and 14.1% of residents were 65 years of age or older. For every 100 females there were 96.6 males, and for every 100 females age 18 and over there were 94.6 males age 18 and over.

95.5% of residents lived in urban areas, while 4.5% lived in rural areas.

There were 196,891 households in the county, of which 31.1% had children under the age of 18 living in them. Of all households, 45.9% were married-couple households, 19.7% were households with a male householder and no spouse or partner present, and 26.7% were households with a female householder and no spouse or partner present. About 30.1% of all households were made up of individuals and 10.2% had someone living alone who was 65 years of age or older. There were 210,184 housing units, of which 6.3% were vacant. Among occupied housing units, 65.7% were owner-occupied and 34.3% were renter-occupied. The homeowner vacancy rate was 1.5% and the rental vacancy rate was 9.4%.

2010 census

As of the 2010 census, there were 430,640 people, 170,197 households, and _ families residing in the county. The population density was 750.5 inhabitants per square mile (289.8/km2). There were 182,262 housing units at an average density of 317.6 per square mile (122.6/km2). The racial makeup of the county was 84.73% White, 6.00% African American, 0.32% Native American, 3.53% Asian, 0.06% Pacific Islander, 2.93% from some other races and 2.42% from two or more races. Hispanic or Latino people of any race were 7.58% of the population.

2000 census

As of the 2000 census, there were 374,601 people, 149,112 households, and 96,624 families residing in the county. The population density was 658.3 inhabitants per square mile (254.2/km2). There were 156,447 housing units at an average density of 275.0 per square mile (106.2/km2). The racial makeup of the county was 88.34% White, 4.84% African American, 0.27% Native American, 2.63% Asian, 0.06% Pacific Islander, 2.22% from some other races and 1.66% from two or more races. Hispanic or Latino people of any race were 4.40% of the population. 25.9% were of German, 10.6% Irish, 9.0% English and 8.4% American ancestry.

Of the 149,112 households 32.20% had children under the age of 18 living with them, 51.00% were married couples living together, 10.30% had a female householder with no husband present, and 35.20% were non-families. 28.10% of households were one person and 8.60% were one person aged 65 or older. The average household size was 2.45 and the average family size was 3.04.

Age spread: 25.70% under the age of 18, 9.40% from 18 to 24, 32.20% from 25 to 44, 21.50% from 45 to 64, and 11.10% 65 or older. The median age was 34 years. For every 100 females, there were 94.20 males. For every 100 females age 18 and over, there were 90.70 males.

The median household income was $46,116 and the median family income was $56,560. Males had a median income of $37,182 versus $28,000 for females. The per capita income for the county was $23,654. About 5.30% of families and 7.90% of the population were below the poverty line, including 9.70% of those under age 18 and 6.40% of those age 65 or over.

Government and infrastructure

The Iowa Department of Corrections Iowa Correctional Institution for Women is in Mitchellville and in Polk County.

Population ranking

The population ranking of the following table is based on the 2020 census of Polk County.

† county seat

Education

School districts include:

Ankeny Community School District, Ankeny

Ballard Community School District, Huxley

Bondurant–Farrar Community School District, Bondurant

Carlisle Community School District, Carlisle

Collins–Maxwell Community School District, Maxwell

Dallas Center–Grimes Community School District, Grimes

Des Moines Independent Community School District, Des Moines

Johnston Community School District, Johnston

Madrid Community School District, Madrid

North Polk Community School District, Alleman

PCM Community School District, Monroe

Saydel Community School District, Des Moines

Southeast Polk Community School District, Pleasant Hill

Urbandale Community School District, Urbandale

West Des Moines Community School District, West Des Moines

Woodward-Granger Community School District, Granger

Attractions

Adventureland Resort

Blank Park Zoo

Casey's Center

Iowa State Capitol

Iowa State Fair

Living History Farms

Science Center of Iowa

Valley Junction

Communities

Census-designated place

Saylorville