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Polk County
Polk County
County
	Polk County Courthouse
	Flag Seal
	Location within the U.S. state of Iowa
	Iowa's location within the U.S.
	Coordinates: 41°41′06″N 93°34′13″W / 41.685°N 93.5703°W
Country	United States
State	Iowa
Founded	January 13, 1846
Named for	James K. Polk
Seat	Des Moines
Largest city	Des Moines
Area
• Total	592 sq mi (1,530 km2)
• Land	574 sq mi (1,490 km2)
• Water	18 sq mi (50 km2) 3.0%
Population (2020)
• Total	492,401
• Estimate (2023)	505,255
• Density	830/sq mi (320/km2)
Time zone	UTC−6 (Central)
• Summer (DST)	UTC−5 (CDT)
Congressional district	3rd
Website	www.polkcountyiowa.gov

Polk County is located in the U.S. state of Iowa. As of the 2020 census, the population was 492,401.^[1] It is Iowa's most populous county, and home to over 15% of the state's residents. The county seat is Des Moines,^[2] which is also the capital city of Iowa. Polk County is included in the Des Moines–West Des Moines, IA Metropolitan Statistical Area.^[3]

History

On January 13, 1846, the legislative body of the Iowa Territory authorized the creation of twelve counties in the Territory,^[4] 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.^[5] 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.^[6]

Geography

According to the United States Census Bureau, the county has a total area of 592 square miles (1,530 km²), of which 574 square miles (1,490 km²) is land and 18 square miles (47 km²) (3.0%) is water.^[7] The county is bisected by the Des Moines River.

Major highways

Transit

Adjacent counties

Boone – northwest
Dallas – west
Jasper – east
Madison – southwest (meeting in a 4-corners)
Marion – southeast
Story – north
Warren – south

Communities

Cities

Census-designated place

Saylorville

Unincorporated communities

Townships

Demographics

Historical population
Census	Pop.	Note	%±
1850	4,513		—
1860	11,625		157.6%
1870	27,857		139.6%
1880	42,395		52.2%
1890	65,410		54.3%
1900	82,624		26.3%
1910	110,438		33.7%
1920	154,029		39.5%
1930	172,837		12.2%
1940	195,835		13.3%
1950	226,010		15.4%
1960	266,315		17.8%
1970	286,101		7.4%
1980	303,170		6.0%
1990	327,140		7.9%
2000	374,601		14.5%
2010	430,640		15.0%
2020	492,401		14.3%
2023 (est.)	505,255	^[8]	2.6%
U.S. Decennial Census^[9] 1790–1960^[10] 1900–1990^[11] 1990–2000^[12] 2010–2020^[1]

Population of Polk County from US census data

2020 census

2022 US Census population pyramid for Polk County from ACS 5-year estimates

As of the census of 2020, there were 492,401 people and 207,290 households in the county, with a population density of 833.5383/sq mi (321.8310/km²). 92.55% of the population reported being of one race. 66.18% were non-Hispanic White, 7.23% were Black, 9.76% were Hispanic, 0.46% were Native American, 4.98% were Asian, 0.06% were Native Hawaiian or Pacific Islander and 11.33% were some other race or more than one race. There were 210,184 housing units, of which 196,891 were occupied.

2010 census

As of the census of 2010, there were 430,640 people and 170,197 households in the county, with a population density of 756.371/sq mi (292.037/km²). There were 182,262 housing units, of which 170,197 were occupied.

2000 census

As of the census of 2000, there were 374,601 people, 149,112 households, and 96,624 families in the county. The population density was 658 inhabitants per square mile (254/km²). There were 156,447 housing units at an average density of 275 per square mile (106/km²). The racial makeup of the county was 88.34% White, 4.84% Black or African American, 0.27% Native American, 2.63% Asian, 0.06% Pacific Islander, 2.22% from other races, and 1.66% from two or more races. 4.40% of the population were Hispanic or Latino of any race. 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.^[13]

United States presidential election results for Polk County, Iowa^[14]
Year	Republican		Democratic		Third party(ies)
Year	No.	%	No.	%	No.	%
2024	112,240	43.70%	140,075	54.54%	4,523	1.76%
2020	106,800	41.27%	146,250	56.52%	5,705	2.20%
2016	93,492	40.38%	119,804	51.74%	18,259	7.89%
2012	96,096	41.98%	128,465	56.13%	4,321	1.89%
2008	89,668	41.82%	120,984	56.43%	3,757	1.75%
2004	95,828	47.29%	105,218	51.93%	1,572	0.78%
2000	79,927	45.89%	89,715	51.51%	4,525	2.60%
1996	60,884	39.00%	83,877	53.73%	11,345	7.27%
1992	63,708	38.09%	78,585	46.98%	24,965	14.93%
1988	57,854	40.42%	84,476	59.01%	814	0.57%
1984	71,413	48.30%	75,413	51.01%	1,022	0.69%
1980	64,156	44.63%	61,984	43.12%	17,618	12.26%
1976	62,316	45.23%	71,917	52.20%	3,530	2.56%
1972	70,245	52.95%	59,169	44.60%	3,245	2.45%
1968	51,814	45.14%	52,731	45.94%	10,239	8.92%
1964	37,280	33.30%	74,194	66.27%	479	0.43%
1960	64,077	53.74%	55,091	46.20%	66	0.06%
1956	62,392	54.02%	53,025	45.91%	74	0.06%
1952	60,934	54.03%	50,867	45.10%	982	0.87%
1948	33,742	41.46%	45,289	55.65%	2,348	2.89%
1944	36,629	44.07%	46,072	55.43%	417	0.50%
1940	41,245	44.26%	51,647	55.42%	301	0.32%
1936	33,819	42.56%	44,274	55.72%	1,367	1.72%
1932	34,023	49.54%	31,517	45.89%	3,132	4.56%
1928	42,290	67.65%	19,725	31.55%	498	0.80%
1924	37,491	62.21%	6,665	11.06%	16,114	26.74%
1920	36,073	66.82%	16,281	30.16%	1,632	3.02%
1916	11,295	45.81%	12,327	50.00%	1,034	4.19%
1912	4,665	20.66%	7,239	32.07%	10,671	47.27%
1908	12,555	58.02%	7,924	36.62%	1,161	5.37%
1904	14,113	72.53%	3,086	15.86%	2,259	11.61%
1900	12,628	64.72%	6,180	31.67%	703	3.60%
1896	11,127	60.24%	7,087	38.37%	257	1.39%
1892	7,757	53.76%	5,538	38.38%	1,133	7.85%
1888	7,049	57.48%	4,966	40.50%	248	2.02%
1884	6,122	56.06%	4,768	43.66%	30	0.27%
1880	4,781	58.50%	2,161	26.44%	1,230	15.05%

Population ranking

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

† county seat

Rank	City/Town/etc.	Municipal type	Population (2020 Census)	Population (2022 Estimate)
1	Des Moines (partially in Warren County)	City	214,133	211,034
2	Ankeny	City	67,887	72,222
3	West Des Moines (partially in Dallas, Warren and Madison Counties)	City	68,723	70,741
4	Urbandale (partially in Dallas County)	City	45,580	46,648
5	Johnston	City	24,064	24,390
6	Altoona	City	19,565	21,503
7	Clive (partially in Dallas County)	City	18,601	18,908
8	Grimes (partially in Dallas County)	City	15,392	16,295
9	Norwalk (mostly in Warren County)	City	12,799	14,177
10	Pleasant Hill	City	10,147	11,186
11	Bondurant	City	7,365	8,710
12	Polk City	City	5,543	6,046
13	Windsor Heights	City	5,252	5,109
14	Carlisle (partially in Warren County)	City	4,160	4,283
15	Saylorville	CDP	3,584	—
16	Mitchellville (partially in Jasper County)	City	2,485	2,493
17	Granger (mostly in Dallas County)	City	1,654	1,951
18	Elkhart	City	882	993
19	Runnells	City	457	448
20	Alleman	City	423	433
21	Sheldahl (partially in Boone and Story Counties)	City	297	301