Iowa Population By County in 2021 (ACS-5Yrs)

Updated on February 28, 2025.

Based on the US Census ACS-5Yrs estimates, in 2021, the total population of Iowa was 3.18M. Among all Iowa counties, Polk was the most populated county (488.87K), followed by Linn (228.57K), and then Scott (174.17K).

On the other hand, the least populated counties were: Adams (3.70K), Ringgold (4.74K), and Audubon (5.66K).

The chart and table below shows the population of each county and the percentage of Iowa population in each county.

You can see similar information for other states and by state for the United States.

Related Topics: Iowa ACS-5Yrs Estimates, 2021 Topic List.

Data Source: US Census - ACS 5-Year Estimates, 2021 Census.

Iowa Population By County in 2021

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County	Population	% of State Population
Adair	7439	0.23
Adams	3697	0.12
Allamakee	14068	0.44
Appanoose	12310	0.39
Audubon	5657	0.18
Benton	25654	0.81
Black Hawk	131396	4.13
Boone	26721	0.84
Bremer	24863	0.78
Buchanan	20598	0.65
Buena Vista	20723	0.65
Butler	14421	0.45
Calhoun	9962	0.31
Carroll	20756	0.65
Cass	13158	0.41
Cedar	18494	0.58
Cerro Gordo	43185	1.36
Cherokee	11606	0.37
Chickasaw	12021	0.38
Clarke	9736	0.31
Clay	16410	0.52
Clayton	17173	0.54
Clinton	46589	1.47
Crawford	16555	0.52
Dallas	96604	3.04
Davis	9066	0.28
Decatur	7718	0.24
Delaware	17508	0.55
Des Moines	39069	1.23
Dickinson	17536	0.55
Dubuque	98687	3.10
Emmet	9433	0.30
Fayette	19582	0.62
Floyd	15672	0.49
Franklin	10056	0.32
Fremont	6702	0.21
Greene	8831	0.28
Grundy	12336	0.39
Guthrie	10599	0.33
Hamilton	15073	0.47
Hancock	10837	0.34
Hardin	16997	0.54
Harrison	14589	0.46
Henry	20488	0.64
Howard	9456	0.30
Humboldt	9622	0.30
Ida	6979	0.22
Iowa	16596	0.52
Jackson	19499	0.61
Jasper	37686	1.19
Jefferson	15846	0.50
Johnson	151833	4.78
Jones	20680	0.65
Keokuk	10050	0.32
Kossuth	14823	0.47
Lee	33724	1.06
Linn	228567	7.19
Louisa	10891	0.34
Lucas	8650	0.27
Lyon	11953	0.38
Madison	16414	0.52
Mahaska	22132	0.70
Marion	33381	1.05
Marshall	40137	1.26
Mills	14658	0.46
Mitchell	10526	0.33
Monona	8732	0.28
Monroe	7589	0.24
Montgomery	10327	0.33
Muscatine	43145	1.36
O'Brien	14139	0.45
Osceola	6168	0.19
Page	15250	0.48
Palo Alto	8996	0.28
Plymouth	25543	0.80
Pocahontas	7091	0.22
Polk	488871	15.38
Pottawattamie	93571	2.94
Poweshiek	18628	0.59
Ringgold	4739	0.15
Sac	9829	0.31
Scott	174170	5.48
Shelby	11750	0.37
Sioux	35647	1.12
Story	98106	3.09
Tama	17079	0.54
Taylor	5932	0.19
Union	12193	0.38
Van Buren	7196	0.23
Wapello	35343	1.11
Warren	51862	1.63
Washington	22525	0.71
Wayne	6504	0.21
Webster	37114	1.17
Winnebago	10743	0.34
Winneshiek	20100	0.63
Woodbury	105102	3.31
Worth	7450	0.23
Wright	12978	0.41