Iowa County Area & Size Rankings

Understanding Iowa’s county areas

The land-area range runs from Dickinson County at 380.5 mi² to Kossuth County at 972.7 mi². The largest has 2.6 times the land area of the smallest and accounts for 1.7% of the combined county land in Iowa. Compare with every state’s largest county.

The median county-equivalent land area is 569.6 mi², below the national median of 604.5 mi². The median describes the middle of the county size distribution; it does not describe how people or development are distributed. A state with a few very large counties can have a much smaller median than its largest entry suggests.

Where water changes the picture

Dickinson County has the most assigned water area, at 23.4 mi². It also has the highest water share, with water making up 5.8% of its total area. Water area and water percentage answer different questions: the first measures an amount, while the second measures the mix of land and water.

Across all 99 entries, water accounts for 0.7% of the combined total area. This is calculated from the summed land and water measurements, rather than averaging county percentages, which would give each small and large county equal weight.

Where people live

An estimated 3,238,387 people lived in Iowa on July 1, 2025 (+1.5% since 2020), or 0.9% of the national total in this dataset. Polk County is the most populous county equivalent, with 516,546 residents — 16% of the state. The largest by land, Kossuth County, has 14,322.

Across the state there are 58 people per square mile of land. County densities range from 902 in Polk County to 8.5 in Adams County; the median county equivalent has 26. Switch the map above to density to see where the state’s population concentrates.

Compare the largest and smallest county equivalents in Iowa to see land, water, and total area on the same scale.

These calculations use the 2026 Census county records listed below. County-equivalent boundaries vary between states; area alone does not measure population, density, or usable land. See coverage and calculation rules.

#	County / equivalent	Land	Water	Water share	Population	Per mi²
1	Kossuth CountyGEOID 19109	972.7 mi²	1.6 mi²	0.2%	14,322	15
2	Pottawattamie CountyGEOID 19155	951.3 mi²	7.9 mi²	0.8%	92,996	98
3	Woodbury CountyGEOID 19193	872.9 mi²	4.9 mi²	0.6%	106,649	122
4	Plymouth CountyGEOID 19149	862.8 mi²	0.8 mi²	0.1%	25,697	30
5	Clayton CountyGEOID 19043	778.5 mi²	14.2 mi²	1.8%	16,845	22
6	Sioux CountyGEOID 19167	767.9 mi²	1.1 mi²	0.1%	36,774	48
7	Fayette CountyGEOID 19065	730.8 mi²	0.5 mi²	0.1%	19,047	26
8	Jasper CountyGEOID 19099	730.4 mi²	2.5 mi²	0.3%	38,153	52
9	Tama CountyGEOID 19171	721 mi²	1.1 mi²	0.1%	16,796	23
10	Linn CountyGEOID 19113	717 mi²	7.7 mi²	1.1%	232,028	324
11	Benton CountyGEOID 19011	716.1 mi²	2.3 mi²	0.3%	26,004	36
12	Webster CountyGEOID 19187	715.7 mi²	2.8 mi²	0.4%	36,838	51
13	Crawford CountyGEOID 19047	714.2 mi²	0.8 mi²	0.1%	16,237	23
14	Harrison CountyGEOID 19085	696.9 mi²	4.8 mi²	0.7%	14,623	21
15	Clinton CountyGEOID 19045	695 mi²	15.2 mi²	2.1%	46,002	66
16	Monona CountyGEOID 19133	694.1 mi²	4.9 mi²	0.7%	8,539	12
17	Winneshiek CountyGEOID 19191	689.8 mi²	0.3 mi²	0%	19,733	29
18	Allamakee CountyGEOID 19005	639.1 mi²	19.7 mi²	3%	14,238	22
19	Jackson CountyGEOID 19097	636 mi²	13.6 mi²	2.1%	19,288	30
20	Johnson CountyGEOID 19103	613 mi²	10.1 mi²	1.6%	160,044	261
21	Dubuque CountyGEOID 19061	608.3 mi²	8.2 mi²	1.3%	99,381	163
22	Shelby CountyGEOID 19165	590.8 mi²	0.6 mi²	0.1%	11,689	20
23	Guthrie CountyGEOID 19077	590.6 mi²	2.4 mi²	0.4%	10,782	18
24	Dallas CountyGEOID 19049	588.2 mi²	3.4 mi²	0.6%	118,457	201
25	Lyon CountyGEOID 19119	587.6 mi²	0.2 mi²	0%	12,354	21
26	Iowa CountyGEOID 19095	586.5 mi²	1 mi²	0.2%	16,504	28
27	Poweshiek CountyGEOID 19157	584.9 mi²	1.1 mi²	0.2%	18,368	31
28	Franklin CountyGEOID 19069	582 mi²	0.6 mi²	0.1%	9,868	17
29	Wright CountyGEOID 19197	580.4 mi²	1.8 mi²	0.3%	12,801	22
30	Butler CountyGEOID 19023	580.1 mi²	1.6 mi²	0.3%	14,049	24
31	Cedar CountyGEOID 19031	579.5 mi²	2.5 mi²	0.4%	18,359	32
32	Keokuk CountyGEOID 19107	579.2 mi²	0.8 mi²	0.1%	9,797	17
33	Delaware CountyGEOID 19055	577.7 mi²	1.2 mi²	0.2%	17,674	31
34	Pocahontas CountyGEOID 19151	577.3 mi²	1.4 mi²	0.2%	6,819	12
35	Cherokee CountyGEOID 19035	576.9 mi²	0.2 mi²	0%	11,369	20
36	Hamilton CountyGEOID 19079	576.7 mi²	0.8 mi²	0.1%	14,944	26
37	Jones CountyGEOID 19105	575.6 mi²	1.5 mi²	0.3%	21,253	37
38	Sac CountyGEOID 19161	575 mi²	3.3 mi²	0.6%	9,525	17
39	Buena Vista CountyGEOID 19021	574.9 mi²	5.3 mi²	0.9%	20,449	36
40	O'Brien CountyGEOID 19141	573 mi²	0.2 mi²	0%	14,220	25
41	Polk CountyGEOID 19153	572.7 mi²	19.2 mi²	3.2%	516,546	902
42	Story CountyGEOID 19169	572.5 mi²	1.1 mi²	0.2%	101,291	177
43	Marshall CountyGEOID 19127	572.5 mi²	0.7 mi²	0.1%	39,890	70
44	Buchanan CountyGEOID 19019	571.1 mi²	2 mi²	0.4%	20,883	37
45	Hancock CountyGEOID 19081	571 mi²	2 mi²	0.4%	10,528	18
46	Mahaska CountyGEOID 19123	570.9 mi²	2.5 mi²	0.4%	21,880	38
47	Boone CountyGEOID 19015	570.5 mi²	3.2 mi²	0.6%	26,799	47
48	Calhoun CountyGEOID 19025	569.8 mi²	2.3 mi²	0.4%	9,562	17
49	Warren CountyGEOID 19181	569.7 mi²	3.3 mi²	0.6%	57,331	101
50	Greene CountyGEOID 19073	569.6 mi²	1.7 mi²	0.3%	8,658	15
51	Carroll CountyGEOID 19027	569.5 mi²	0.8 mi²	0.1%	20,303	36
52	Hardin CountyGEOID 19083	569.3 mi²	0.7 mi²	0.1%	16,455	29
53	Adair CountyGEOID 19001	569.3 mi²	1 mi²	0.2%	7,403	13
54	Washington CountyGEOID 19183	568.8 mi²	2.1 mi²	0.4%	22,667	40
55	Cerro Gordo CountyGEOID 19033	568.3 mi²	6.8 mi²	1.2%	42,372	75
56	Clay CountyGEOID 19041	567.2 mi²	5.4 mi²	0.9%	16,202	29
57	Black Hawk CountyGEOID 19013	565.8 mi²	6.9 mi²	1.2%	131,532	232
58	Cass CountyGEOID 19029	564.3 mi²	0.7 mi²	0.1%	12,960	23
59	Palo Alto CountyGEOID 19147	563.9 mi²	5.6 mi²	1%	8,899	16
60	Madison CountyGEOID 19121	561 mi²	1.2 mi²	0.2%	17,270	31
61	Marion CountyGEOID 19125	554.5 mi²	16 mi²	2.8%	34,192	62
62	Ringgold CountyGEOID 19159	535.5 mi²	3.4 mi²	0.6%	4,642	8.7
63	Page CountyGEOID 19145	534.9 mi²	0.5 mi²	0.1%	14,856	28
64	Taylor CountyGEOID 19173	531.9 mi²	2.8 mi²	0.5%	5,835	11
65	Decatur CountyGEOID 19053	531.9 mi²	1.6 mi²	0.3%	7,655	14
66	Wayne CountyGEOID 19185	525.5 mi²	1.7 mi²	0.3%	6,738	13
67	Lee CountyGEOID 19111	517.6 mi²	21.3 mi²	4%	32,306	62
68	Fremont CountyGEOID 19071	511.2 mi²	5.5 mi²	1.1%	6,522	13
69	Chickasaw CountyGEOID 19037	504.3 mi²	1.3 mi²	0.3%	11,663	23
70	Davis CountyGEOID 19051	502.2 mi²	2.7 mi²	0.5%	9,230	18
71	Grundy CountyGEOID 19075	501.9 mi²	0 mi²	0%	12,361	25
72	Floyd CountyGEOID 19067	500.6 mi²	0.8 mi²	0.2%	14,901	30
73	Appanoose CountyGEOID 19007	497.3 mi²	19 mi²	3.7%	12,077	24
74	Van Buren CountyGEOID 19177	484.8 mi²	5.7 mi²	1.2%	7,131	15
75	Howard CountyGEOID 19089	473.2 mi²	0.4 mi²	0.1%	9,415	20
76	Mitchell CountyGEOID 19131	469.3 mi²	0.4 mi²	0.1%	10,650	23
77	Scott CountyGEOID 19163	458.1 mi²	10.1 mi²	2.2%	175,259	383
78	Audubon CountyGEOID 19009	443 mi²	0.4 mi²	0.1%	5,509	12
79	Muscatine CountyGEOID 19139	437.4 mi²	11.7 mi²	2.6%	41,853	96
80	Mills CountyGEOID 19129	437.4 mi²	3.2 mi²	0.7%	14,793	34
81	Jefferson CountyGEOID 19101	435.5 mi²	1.4 mi²	0.3%	15,291	35
82	Bremer CountyGEOID 19017	435.5 mi²	3.9 mi²	0.9%	25,296	58
83	Humboldt CountyGEOID 19091	434.4 mi²	1.3 mi²	0.3%	9,409	22
84	Henry CountyGEOID 19087	434.3 mi²	2.2 mi²	0.5%	19,349	45
85	Monroe CountyGEOID 19135	433.7 mi²	0.6 mi²	0.1%	7,406	17
86	Wapello CountyGEOID 19179	431.8 mi²	4.2 mi²	1%	35,210	82
87	Ida CountyGEOID 19093	431.5 mi²	0.5 mi²	0.1%	6,777	16
88	Clarke CountyGEOID 19039	431.1 mi²	0.6 mi²	0.1%	9,574	22
89	Lucas CountyGEOID 19117	430.7 mi²	3.8 mi²	0.9%	8,847	21
90	Montgomery CountyGEOID 19137	424.1 mi²	0.9 mi²	0.2%	10,002	24
91	Union CountyGEOID 19175	423.6 mi²	2.2 mi²	0.5%	11,829	28
92	Adams CountyGEOID 19003	423.4 mi²	2.1 mi²	0.5%	3,617	8.5
93	Des Moines CountyGEOID 19057	416.1 mi²	13.6 mi²	3.2%	38,077	92
94	Louisa CountyGEOID 19115	401.8 mi²	15.7 mi²	3.8%	10,416	26
95	Winnebago CountyGEOID 19189	400.5 mi²	1.2 mi²	0.3%	10,251	26
96	Worth CountyGEOID 19195	400.1 mi²	1.8 mi²	0.5%	7,338	18
97	Osceola CountyGEOID 19143	398.7 mi²	0.7 mi²	0.2%	5,980	15
98	Emmet CountyGEOID 19063	395.9 mi²	6.6 mi²	1.6%	9,107	23
99	Dickinson CountyGEOID 19059	380.5 mi²	23.4 mi²	5.8%	18,077	48

County / equivalent

Land

Water

Water share

Population

Per mi²

Kossuth CountyGEOID 19109

972.7 mi²

1.6 mi²

0.2%

14,322

Pottawattamie CountyGEOID 19155

951.3 mi²

7.9 mi²

0.8%

92,996

Woodbury CountyGEOID 19193

872.9 mi²

4.9 mi²

0.6%

106,649

122

Plymouth CountyGEOID 19149

862.8 mi²

0.8 mi²

0.1%

25,697

Clayton CountyGEOID 19043

778.5 mi²

14.2 mi²

1.8%

16,845

Sioux CountyGEOID 19167

767.9 mi²

1.1 mi²

0.1%

36,774

Fayette CountyGEOID 19065

730.8 mi²

0.5 mi²

0.1%

19,047

Jasper CountyGEOID 19099

730.4 mi²

2.5 mi²

0.3%

38,153

Tama CountyGEOID 19171

721 mi²

1.1 mi²

0.1%

16,796

Linn CountyGEOID 19113

717 mi²

7.7 mi²

1.1%

232,028

324

Benton CountyGEOID 19011

716.1 mi²

2.3 mi²

0.3%

26,004

Webster CountyGEOID 19187

715.7 mi²

2.8 mi²

0.4%

36,838

Crawford CountyGEOID 19047

714.2 mi²

0.8 mi²

0.1%

16,237

Harrison CountyGEOID 19085

696.9 mi²

4.8 mi²

0.7%

14,623

Clinton CountyGEOID 19045

695 mi²

15.2 mi²

2.1%

46,002

Monona CountyGEOID 19133

694.1 mi²

4.9 mi²

0.7%

8,539

Winneshiek CountyGEOID 19191

689.8 mi²

0.3 mi²

19,733

Allamakee CountyGEOID 19005

639.1 mi²

19.7 mi²

14,238

Jackson CountyGEOID 19097

636 mi²

13.6 mi²

2.1%

19,288

Johnson CountyGEOID 19103

613 mi²

10.1 mi²

1.6%

160,044

261

Dubuque CountyGEOID 19061

608.3 mi²

8.2 mi²

1.3%

99,381

163

Shelby CountyGEOID 19165

590.8 mi²

0.6 mi²

0.1%

11,689

Guthrie CountyGEOID 19077

590.6 mi²

2.4 mi²

0.4%

10,782

Dallas CountyGEOID 19049

588.2 mi²

3.4 mi²

0.6%

118,457

201

Lyon CountyGEOID 19119

587.6 mi²

0.2 mi²

12,354

Iowa CountyGEOID 19095

586.5 mi²

1 mi²

0.2%

16,504

Poweshiek CountyGEOID 19157

584.9 mi²

1.1 mi²

0.2%

18,368

Franklin CountyGEOID 19069

582 mi²

0.6 mi²

0.1%

9,868

Wright CountyGEOID 19197

580.4 mi²

1.8 mi²

0.3%

12,801

Butler CountyGEOID 19023

580.1 mi²

1.6 mi²

0.3%

14,049

Cedar CountyGEOID 19031

579.5 mi²

2.5 mi²

0.4%

18,359

Keokuk CountyGEOID 19107

579.2 mi²

0.8 mi²

0.1%

9,797

Delaware CountyGEOID 19055

577.7 mi²

1.2 mi²

0.2%

17,674

Pocahontas CountyGEOID 19151

577.3 mi²

1.4 mi²

0.2%

6,819

Cherokee CountyGEOID 19035

576.9 mi²

0.2 mi²

11,369

Hamilton CountyGEOID 19079

576.7 mi²

0.8 mi²

0.1%

14,944

Jones CountyGEOID 19105

575.6 mi²

1.5 mi²

0.3%

21,253

Sac CountyGEOID 19161

575 mi²

3.3 mi²

0.6%

9,525

Buena Vista CountyGEOID 19021

574.9 mi²

5.3 mi²

0.9%

20,449

O'Brien CountyGEOID 19141

573 mi²

0.2 mi²

14,220

Polk CountyGEOID 19153

572.7 mi²

19.2 mi²

3.2%

516,546

902

Story CountyGEOID 19169

572.5 mi²

1.1 mi²

0.2%

101,291

177

Marshall CountyGEOID 19127

572.5 mi²

0.7 mi²

0.1%

39,890

Buchanan CountyGEOID 19019

571.1 mi²

2 mi²

0.4%

20,883

Hancock CountyGEOID 19081

571 mi²

2 mi²

0.4%

10,528

Mahaska CountyGEOID 19123

570.9 mi²

2.5 mi²

0.4%

21,880

Boone CountyGEOID 19015

570.5 mi²

3.2 mi²

0.6%

26,799

Calhoun CountyGEOID 19025

569.8 mi²

2.3 mi²

0.4%

9,562

Warren CountyGEOID 19181

569.7 mi²

3.3 mi²

0.6%

57,331

101

Greene CountyGEOID 19073

569.6 mi²

1.7 mi²

0.3%

8,658

Carroll CountyGEOID 19027

569.5 mi²

0.8 mi²

0.1%

20,303

Hardin CountyGEOID 19083

569.3 mi²

0.7 mi²

0.1%

16,455

Adair CountyGEOID 19001

569.3 mi²

1 mi²

0.2%

7,403

Washington CountyGEOID 19183

568.8 mi²

2.1 mi²

0.4%

22,667

Cerro Gordo CountyGEOID 19033

568.3 mi²

6.8 mi²

1.2%

42,372

Clay CountyGEOID 19041

567.2 mi²

5.4 mi²

0.9%

16,202

Black Hawk CountyGEOID 19013

565.8 mi²

6.9 mi²

1.2%

131,532

232

Cass CountyGEOID 19029

564.3 mi²

0.7 mi²

0.1%

12,960

Palo Alto CountyGEOID 19147

563.9 mi²

5.6 mi²

8,899

Madison CountyGEOID 19121

561 mi²

1.2 mi²

0.2%

17,270

Marion CountyGEOID 19125

554.5 mi²

16 mi²

2.8%

34,192

Ringgold CountyGEOID 19159

535.5 mi²

3.4 mi²

0.6%

4,642

8.7

Page CountyGEOID 19145

534.9 mi²

0.5 mi²

0.1%

14,856

Taylor CountyGEOID 19173

531.9 mi²

2.8 mi²

0.5%

5,835

Decatur CountyGEOID 19053

531.9 mi²

1.6 mi²

0.3%

7,655

Wayne CountyGEOID 19185

525.5 mi²

1.7 mi²

0.3%

6,738

Lee CountyGEOID 19111

517.6 mi²

21.3 mi²

32,306

Fremont CountyGEOID 19071

511.2 mi²

5.5 mi²

1.1%

6,522

Chickasaw CountyGEOID 19037

504.3 mi²

1.3 mi²

0.3%

11,663

Davis CountyGEOID 19051

502.2 mi²

2.7 mi²

0.5%

9,230

Grundy CountyGEOID 19075

501.9 mi²

0 mi²

12,361

Floyd CountyGEOID 19067

500.6 mi²

0.8 mi²

0.2%

14,901

Appanoose CountyGEOID 19007

497.3 mi²

19 mi²

3.7%

12,077

Van Buren CountyGEOID 19177

484.8 mi²

5.7 mi²

1.2%

7,131

Howard CountyGEOID 19089

473.2 mi²

0.4 mi²

0.1%

9,415

Mitchell CountyGEOID 19131

469.3 mi²

0.4 mi²

0.1%

10,650

Scott CountyGEOID 19163

458.1 mi²

10.1 mi²

2.2%

175,259

383

Audubon CountyGEOID 19009

443 mi²

0.4 mi²

0.1%

5,509

Muscatine CountyGEOID 19139

437.4 mi²

11.7 mi²

2.6%

41,853

Mills CountyGEOID 19129

437.4 mi²

3.2 mi²

0.7%

14,793

Jefferson CountyGEOID 19101

435.5 mi²

1.4 mi²

0.3%

15,291

Bremer CountyGEOID 19017

435.5 mi²

3.9 mi²

0.9%

25,296

Humboldt CountyGEOID 19091

434.4 mi²

1.3 mi²

0.3%

9,409

Henry CountyGEOID 19087

434.3 mi²

2.2 mi²

0.5%

19,349

Monroe CountyGEOID 19135

433.7 mi²

0.6 mi²

0.1%

7,406

Wapello CountyGEOID 19179

431.8 mi²

4.2 mi²

35,210

Ida CountyGEOID 19093

431.5 mi²

0.5 mi²

0.1%

6,777

Clarke CountyGEOID 19039

431.1 mi²

0.6 mi²

0.1%

9,574

Lucas CountyGEOID 19117

430.7 mi²

3.8 mi²

0.9%

8,847

Montgomery CountyGEOID 19137

424.1 mi²

0.9 mi²

0.2%

10,002

Union CountyGEOID 19175

423.6 mi²

2.2 mi²

0.5%

11,829

Adams CountyGEOID 19003

423.4 mi²

2.1 mi²

0.5%

3,617

8.5

Des Moines CountyGEOID 19057

416.1 mi²

13.6 mi²

3.2%

38,077

Louisa CountyGEOID 19115

401.8 mi²

15.7 mi²

3.8%

10,416

Winnebago CountyGEOID 19189

400.5 mi²

1.2 mi²

0.3%

10,251

Worth CountyGEOID 19195

400.1 mi²

1.8 mi²

0.5%

7,338

Osceola CountyGEOID 19143

398.7 mi²

0.7 mi²

0.2%

5,980

Emmet CountyGEOID 19063

395.9 mi²

6.6 mi²

1.6%

9,107

Dickinson CountyGEOID 19059

380.5 mi²

23.4 mi²

5.8%

18,077

Iowa counties by area

Understanding Iowa’s county areas

Where water changes the picture

Where people live

Complete area table