Iowa population by county: July 2025 Census estimates for all 99 counties, change since 2020, density, and a link to each official parcel map.
Looking for Iowa population by county? The Census Bureau estimates that Iowa had 3,238,387 residents on July 1, 2025, spread across 99 counties. Polk County is the most populous, with 516,546 people (16% of the state), and Adams County is the least populous, with 3,617.
The table below lists every county with its 2025 estimate, its April 2020 starting point, the change, people per square mile, and a link to its official parcel viewer.
Percent change runs from the April 1, 2020 estimates base to July 1, 2025. People per square mile is the July 2025 estimate divided by the county's land area in the Census Bureau's 2020 Gazetteer file, so lakes and bays are left out.
How Iowa's population is spread out
Grouping the counties by size shows how concentrated the state is:
Residents (July 2025)
Counties
Total residents
Share of state
250,000 to 999,999
1
516,546
16%
100,000 to 249,999
7
1,025,260
32%
25,000 to 99,999
18
775,171
24%
10,000 to 24,999
46
711,608
22%
Under 10,000
27
209,802
6%
1 county with at least 250,000 residents holds 16% of the state's population.
Most and least densely populated
The most crowded counties by people per square mile of land:
Polk County: 903 per sq mi (516,546 people on 572 sq mi)
Scott County: 383 per sq mi (175,259 people on 458 sq mi)
Linn County: 324 per sq mi (232,028 people on 717 sq mi)
Johnson County: 261 per sq mi (160,044 people on 613 sq mi)
Black Hawk County: 232 per sq mi (131,532 people on 566 sq mi)
The most thinly settled:
Adams County: 8.5 per sq mi (3,617 people on 423 sq mi)
Ringgold County: 8.7 per sq mi (4,642 people on 535 sq mi)
Taylor County: 11 per sq mi (5,835 people on 532 sq mi)
Pocahontas County: 12 per sq mi (6,819 people on 577 sq mi)
Monona County: 12 per sq mi (8,539 people on 694 sq mi)
About these numbers
They are estimates. Between censuses the Census Bureau's Population Estimates Program updates county totals each year from births, deaths and migration records. The next full count is the 2030 census.
The base is April 1, 2020. The estimates start from an April 1, 2020 "estimates base" built from the 2020 census, which is why it is slightly different from the published census count.
Each new release revises the past. A newer vintage can change earlier years as well, so compare numbers from the same release, as this page does.
Statewide total. The counties add up exactly to the statewide figure of 3,238,387 in the same file.
Using population numbers in a land search
Big counties, busy offices. In the most populous counties, parcel maps and deed records are usually online and searchable, but recording and permit offices are busier. Allow for that if you are on a deadline.
Small counties, fewer sales. In counties with only a few thousand people, land changes hands less often, so there are fewer recent sales to compare a price with. Recorded deeds and the local assessor's sales records are the best source.
Density hints at lot size. A low people-per-square-mile figure usually means farms, ranches and timber tracts; a high one means subdivided lots. The parcel viewer shows the actual parcel lines.
Check the official map. Use the parcel viewer link in the table for boundaries, parcel numbers and owner names, then confirm anything important with the local assessor and the office that records deeds.