County facts · Population growth · October 23, 2026
Fastest Growing Counties in Iowa, 2020 to 2025
Iowa's fastest growing counties by percent and by people added, April 2020 to July 2025 Census estimates, with each official parcel map.
Looking for the fastest growing counties in Iowa? From the Census Bureau's April 1, 2020 estimates base to its July 1, 2025 estimate, Iowa went from about 3,190,582 to 3,238,387 residents, a change of +47,805 (+1.5%). The fastest growing county by percentage was Dallas County (+18.8%), while Polk County added the most people (+24,157, +4.9%).
Each table links the county's Platbookmapper page and its official parcel viewer, so you can go from the growth numbers straight to the property lines.
Iowa growth at a glance
- County: 99
- Statewide, April 2020 to July 2025: +47,805 residents (+1.5%); July 2024 to July 2025 alone: +7,933 (+0.2%)
- Grew: 33 of 99 · Lost residents: 66
- Fastest growing by percent: Dallas County (+18.8%); most people added: Polk County (+24,157)
- Counties with more deaths than births over the period: 74 of 99
The 10 fastest growing Iowa counties by percent
| # | County | Apr 2020 | Jul 2025 | Change | % change | Parcel viewer |
|---|---|---|---|---|---|---|
| 1 | Dallas County | 99,721 | 118,457 | +18,736 | +18.8% | county web map |
| 2 | Warren County | 52,401 | 57,331 | +4,930 | +9.4% | Beacon (Schneider Geospatial) |
| 3 | Polk County | 492,389 | 516,546 | +24,157 | +4.9% | ArcGIS Web AppBuilder |
| 4 | Johnson County | 152,864 | 160,044 | +7,180 | +4.7% | Beacon (Schneider Geospatial) |
| 5 | Madison County | 16,547 | 17,270 | +723 | +4.4% | Beacon (Schneider Geospatial) |
| 6 | Wayne County | 6,498 | 6,738 | +240 | +3.7% | CAMAvision Maps |
| 7 | Lyon County | 11,932 | 12,354 | +422 | +3.5% | Beacon (Schneider Geospatial) |
| 8 | Jones County | 20,648 | 21,253 | +605 | +2.9% | Beacon (Schneider Geospatial) |
| 9 | Story County | 98,541 | 101,291 | +2,750 | +2.8% | Beacon (Schneider Geospatial) |
| 10 | Sioux County | 35,869 | 36,774 | +905 | +2.5% | Beacon (Schneider Geospatial) |
These 10 added about 60,648 people combined. The median county changed by −1.1%.
The 10 counties that added the most people
| # | County | People added | % change | Jul 2025 | Parcel viewer |
|---|---|---|---|---|---|
| 1 | Polk County | +24,157 | +4.9% | 516,546 | ArcGIS Web AppBuilder |
| 2 | Dallas County | +18,736 | +18.8% | 118,457 | county web map |
| 3 | Johnson County | +7,180 | +4.7% | 160,044 | Beacon (Schneider Geospatial) |
| 4 | Warren County | +4,930 | +9.4% | 57,331 | Beacon (Schneider Geospatial) |
| 5 | Story County | +2,750 | +2.8% | 101,291 | Beacon (Schneider Geospatial) |
| 6 | Linn County | +1,737 | +0.8% | 232,028 | county web map |
| 7 | Sioux County | +905 | +2.5% | 36,774 | Beacon (Schneider Geospatial) |
| 8 | Marion County | +770 | +2.3% | 34,192 | Beacon (Schneider Geospatial) |
| 9 | Madison County | +723 | +4.4% | 17,270 | Beacon (Schneider Geospatial) |
| 10 | Woodbury County | +668 | +0.6% | 106,649 | Beacon (Schneider Geospatial) |
The top 10 account for about 92% of all the gains in the counties that grew.
Where the new residents came from
The Census Bureau splits each change into natural change (births minus deaths), net domestic migration (moves from other parts of the US) and net international migration. Totals for April 2020 to July 2025 in the five fastest growing counties:
| County | Births minus deaths | Net domestic moves | Net international moves | Total change |
|---|---|---|---|---|
| Dallas County | +3,854 | +12,787 | +2,079 | +18,736 |
| Warren County | +440 | +4,353 | +121 | +4,930 |
| Polk County | +10,812 | +1,905 | +11,391 | +24,157 |
| Johnson County | +4,119 | −1,145 | +4,124 | +7,180 |
| Madison County | +81 | +621 | +17 | +723 |
In 3 of these 5, moves from elsewhere in the US were the biggest source of growth. The three parts do not add up exactly to the total because the Census Bureau also carries a small residual.
The last year alone: July 2024 to July 2025
- Dallas County: +3.2% (+3,645)
- Wayne County: +1.6% (+104)
- Warren County: +1.5% (+835)
- Guthrie County: +0.9% (+95)
- Buchanan County: +0.8% (+172)
3 of these 5 are also in the 2020–2025 top 10, so the growth is not a one-year blip.
Counties losing residents
66 of Iowa's 99 counties had fewer residents in July 2025 than in April 2020. The steepest declines:
- Henry County: −5.5% (−1,133, now about 19,349)
- Floyd County: −4.7% (−728, now about 14,901)
- Winnebago County: −4.0% (−423, now about 10,251)
- Louisa County: −3.9% (−422, now about 10,416)
- Lee County: −3.7% (−1,246, now about 32,306)
What fast growth means on a parcel map
- New lots show up as plats first. When land is subdivided, the plat is recorded with the county and the parcel layer catches up on its own schedule, so a brand-new lot may not appear on the map for a while. Check the recorder's recent plats if a parcel looks missing.
- Parcel numbers change after splits. A tract that was one parcel last year can be several today. Search by owner name or address as well as by an old parcel number.
- City limits move. Growing cities annex land, which changes who handles zoning and permits even though the county still keeps the deed and the tax map.
- Percent is not the same as people. A small county can post a big percentage on a modest number of new residents, so read the people-added column too.
Related guides
- Largest counties in Iowa
- Iowa county GIS websites by viewer
- Iowa landowner maps for hunting
- Fastest growing counties in the US
- US counties losing population
More: All Iowa counties on Platbookmapper
Sources
- U.S. Census Bureau, Population Estimates Program, county totals, Vintage 2025 (April 1, 2020 estimates base and July 1, 2020–2025 estimates, with components of change). Percent change is from the April 1, 2020 estimates base to the July 1, 2025 estimate.
- Platbookmapper county GIS directory (live data file behind our county pages, pulled October 23, 2026) for each official parcel viewer.