IA · 2026 Census Gazetteer

Iowa counties by area

Official, comparable measurements for 99 counties and county equivalents.

Source fields preservedGEOID · ALAND · AWATER

County equivalents99

Combined land55,853.7 mi²

Combined water419 mi²

Largest by landKossuth County

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.

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.

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.

Complete area table

Sorted from largest to smallest land area.

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

How to read this table. Land and water areas are Census statistical measurements in square miles. Adding county rows can differ slightly from separately published state totals because of rounding and geographic treatment.