County Maps US

Jefferson County, Iowa

A county in Iowa, ranked 48 of 99 by population.

CountyFIPS 19101

Within Iowa
Jefferson County, highlighted, with the areas around it. Boundaries generalised from the 2025 Census cartographic boundary file; neighbour fills carry no data. The dot marks Fairfield, the county seat, located via the 2025 Census Gazetteer.

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Population
15,291
-397 (-2.5%) since 2020
Land area
435.5
square miles. A further 0.3% of the total area is water
Population density
35.1
people per square mile, computed rather than published
County seat
Fairfield
Seat of county government.
Established
1839
186 years ago
Largest city
Fairfield city
Population 9,220.

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; Wikidata (CC0), Wikidata. Retrieved 30 August 2026.

Satellite view

Aerial imagery of Jefferson County with its boundary drawn on top. A map shows you the shape; this shows you what is inside it, and which side of the line a place falls on.

Aerial view of Jefferson County, Iowa from the USGS National Map, with its boundary outlined
Imagery: USGS National Map, USGS Imagery Only, public domain, requested from USGS by your browser when you reach this point on the page, at 800 by 625 pixels. The boundary is the 2025 Census cartographic boundary file, reprojected to Web Mercator to match the imagery. You can also open the USGS National Map viewer.

Where Jefferson County ranks

Position among the 99 counties of Iowa, and among all 3,144 US counties and county-equivalents. Computed from the figures on this page.

MeasureValueIn IowaNationally
Population15,29148th of 992,074th of 3,144
Land area435.5 sq mi81st of 992,326th of 3,144
Population density35.1 per sq mi34th of 991,792nd of 3,144
Median household income$61,62091st of 991,925th of 3,143

Full data for Jefferson County

Every figure below is attributed to the Census Bureau product it came from, with the vintage of that product.
MeasureValueSource and vintage
Population15,291Vintage 2025 Population Estimates
Population in 202015,688Vintage 2025 Population Estimates
2020 estimates base?15,662Vintage 2025 Population Estimates
Land area435.5 sq mi2025 Gazetteer Files
Water area1.4 sq mi2025 Gazetteer Files
Total area436.9 sq mi2025 Gazetteer Files
Population density?35.1 per sq miComputed: Vintage 2025 estimates divided by 2025 Gazetteer land area
Median household income$61,620American Community Survey 2020-2024 5-Year Estimates
Median home value$163,400American Community Survey 2020-2024 5-Year Estimates
Median age43.7American Community Survey 2020-2024 5-Year Estimates
Households6,952American Community Survey 2020-2024 5-Year Estimates
Housing units7,706American Community Survey 2020-2024 5-Year Estimates

Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026. Population density is computed here, not published: it divides the Vintage 2025 population estimate by the 2025 Gazetteer land area, which are two different Census products. Retrieved 30 August 2026.

How the population changed

The Census Bureau publishes the components behind an estimate, not just the total. For the year to July 2025:

Births minus deaths
-52
131 births, 183 deaths
Net migration
-59
More people moved out than moved in.

Source: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026. Retrieved 30 August 2026.

The 6 areas bordering Jefferson County

Ordered by the length of the border actually shared, which the Census Bureau publishes in its county adjacency file and which no other county reference presents.

Bordering areaStateShared borderPopulation
Van Buren CountyIowa24 mi7,131
Wapello CountyIowa18 mi35,210
Henry CountyIowa18 mi19,349
Keokuk CountyIowa12 mi9,797
Washington CountyIowa12 mi22,667
Davis CountyIowaa single point9,230

Source: US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. Retrieved 30 August 2026.

All 99 counties of Iowa

Open the interactive Iowa county map, or jump straight to any of them.

Data on this page last rebuilt 30 August 2026. How these figures are produced.