Data / Rankings / Median Air Quality Index (US EPA) / Counties in Wisconsin

Counties in Wisconsin by median Air Quality Index (US EPA)

La Crosse County had the highest median Air Quality Index (US EPA) of 34 counties in 2005, at 68. Eau Claire County had the lowest, at 12. The median was 44. Source: the U.S. Environmental Protection Agency.

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Highest68La Crosse County
Lowest12Eau Claire County
Median4434 counties

Map of counties, 2005

Ashland County: 33 indexBrown County: 44 indexColumbia County: 44 indexDane County: 49 indexDodge County: 52 indexDoor County: 42 indexDouglas County: 19 indexEau Claire County: 12 indexFlorence County: 39 indexFond du Lac County: 44 indexForest County: 37 indexGrant County: 52 indexJefferson County: 45 indexKenosha County: 52 indexKewaunee County: 40 indexLa Crosse County: 68 indexManitowoc County: 44 indexMarathon County: 43 indexMilwaukee County: 45 indexOneida County: 41 indexOutagamie County: 44 indexOzaukee County: 45 indexRacine County: 42 indexRock County: 44 indexSt. Croix County: 39 indexSauk County: 42 indexSheboygan County: 42 indexTaylor County: 37 indexVernon County: 44 indexVilas County: 41 indexWalworth County: 46 indexWashington County: 42 indexWaukesha County: 43 indexWaupaca County: 48 index
  • Under 39
  • 39 to 42
  • 42 to 44
  • 44 to 47
  • 47 and over
  • No data
index, 2005. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2005

La Crosse County: 68 indexLa Crosse County68Dodge County: 52 indexDodge County52Grant County: 52 indexGrant County52Kenosha County: 52 indexKenosha County52Dane County: 49 indexDane County49Waupaca County: 48 indexWaupaca County48Walworth County: 46 indexWalworth County46Jefferson County: 45 indexJefferson County45Milwaukee County: 45 indexMilwaukee County45Ozaukee County: 45 indexOzaukee County45Brown County: 44 indexBrown County44Columbia County: 44 indexColumbia County44Fond du Lac County: 44 indexFond du Lac County44Manitowoc County: 44 indexManitowoc County44Outagamie County: 44 indexOutagamie County44Rock County: 44 indexRock County44Vernon County: 44 indexVernon County44Marathon County: 43 indexMarathon County43Waukesha County: 43 indexWaukesha County43Door County: 42 indexDoor County42Racine County: 42 indexRacine County42Sauk County: 42 indexSauk County42Sheboygan County: 42 indexSheboygan County42Washington County: 42 indexWashington County42Oneida County: 41 indexOneida County41Vilas County: 41 indexVilas County41Kewaunee County: 40 indexKewaunee County40Florence County: 39 indexFlorence County39St. Croix County: 39 indexSt. Croix County39Forest County: 37 indexForest County37Taylor County: 37 indexTaylor County37Ashland County: 33 indexAshland County33Douglas County: 19 indexDouglas County19Eau Claire County: 12 indexEau Claire County12La Crosse County: 68 indexLa Crosse County68Dodge County: 52 indexDodge County52Grant County: 52 indexGrant County52Kenosha County: 52 indexKenosha County52Dane County: 49 indexDane County49Waupaca County: 48 indexWaupaca County48Walworth County: 46 indexWalworth County46Jefferson County: 45 indexJefferson County45Milwaukee County: 45 indexMilwaukee County45Ozaukee County: 45 indexOzaukee County45Brown County: 44 indexBrown County44Columbia County: 44 indexColumbia County44Fond du Lac County: 44 indexFond du Lac County44Manitowoc County: 44 indexManitowoc County44Outagamie County: 44 indexOutagamie County44Rock County: 44 indexRock County44Vernon County: 44 indexVernon County44Marathon County: 43 indexMarathon County43Waukesha County: 43 indexWaukesha County43Door County: 42 indexDoor County42Racine County: 42 indexRacine County42Sauk County: 42 indexSauk County42Sheboygan County: 42 indexSheboygan County42Washington County: 42 indexWashington County42Oneida County: 41 indexOneida County41Vilas County: 41 indexVilas County41Kewaunee County: 40 indexKewaunee County40Florence County: 39 indexFlorence County39St. Croix County: 39 indexSt. Croix County39Forest County: 37 indexForest County37Taylor County: 37 indexTaylor County37Ashland County: 33 indexAshland County33Douglas County: 19 indexDouglas County19Eau Claire County: 12 indexEau Claire County12
index. Source: EPA, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12.

Full ranking

RankCounties2005
index		Change on 2004
1La Crosse County68n/a
2Dodge County52+6
2Grant County520
2Kenosha County52+8
5Dane County49+7
6Waupaca County48+6
7Walworth County46+6
8Jefferson County45+6
8Milwaukee County45+5
8Ozaukee County45+6
11Brown County44+4
11Columbia County44+6
11Fond du Lac County44+7
11Manitowoc County44+4
11Outagamie County44+3
11Rock County44+4
11Vernon County44+7
18Marathon County43+3
18Waukesha County43+4
20Door County42+3
20Racine County42+7
20Sauk County42+4
20Sheboygan County42+5
20Washington County42+4
25Oneida County41+3
25Vilas County41+2
27Kewaunee County40+2
28Florence County39+2
28St. Croix County39+2
30Forest County37+1
30Taylor County37+2
32Ashland County33+3
33Douglas County19+3
34Eau Claire County12+1

Other periods

About this ranking

Median of the daily Air Quality Index (AQI) values of a US county over the days of the year with an AQI, from the EPA AirData annual summaries.

More on how it is measured
  • The daily county AQI is the highest AQI among the monitors and pollutants reported that day (ozone, PM2.5, PM10, carbon monoxide and nitrogen dioxide).
  • Lower is cleaner: 0 to 50 is good, 51 to 100 moderate and above 100 unhealthy for sensitive groups.

United States counties with air quality monitors only, about 1,000 of some 3,100 in recent years; a county without monitors has no value. The number of days with an AQI differs between counties because some monitors run only in the ozone season.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. 14 counties with data in other periods have no value for 2005 and are left out rather than filled from another source. Equal values share a rank.

How to cite

U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Environmental Protection Agency. (2026). EPA AirData annual AQI by county: median daily AQI (Counties in Wisconsin by median Air Quality Index (US EPA), 2005) [Data set]. Retrieved October 12, 2026, from https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual

MLA 9

EPA AirData annual AQI by county: median daily AQI, Counties in Wisconsin by median Air Quality Index (US EPA), 2005. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/median-air-quality-index/wisconsin-counties?period=2005. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: median daily AQI. Counties in Wisconsin by median Air Quality Index (US EPA), 2005. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/median-air-quality-index/wisconsin-counties?period=2005.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: median daily AQI, Counties in Wisconsin by median Air Quality Index (US EPA), 2005 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/median-air-quality-index/wisconsin-counties?period=2005 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_wisconsin_by_2005,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: median daily AQI: Counties in Wisconsin by median Air Quality Index (US EPA), 2005}},
  year = {2026},
  howpublished = {Data set},
  url = {https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/wisconsin-counties?period=2005. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download\_files.html\#Annual. Retrieved 2026-10-12.},
}
RIS
TY  - DATA
AU  - U.S. Environmental Protection Agency
TI  - EPA AirData annual AQI by county: median daily AQI: Counties in Wisconsin by median Air Quality Index (US EPA), 2005
PY  - 2026
DA  - 2026/07/13
PB  - U.S. Environmental Protection Agency
DB  - Invokely
UR  - https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual
L2  - https://invokely.ai/rankings/median-air-quality-index/wisconsin-counties?period=2005
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/median-air-quality-index/wisconsin-counties?period=2005.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: median daily AQI. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Questions

Which county has the highest median Air Quality Index (US EPA)?

La Crosse County, with 68 in 2005, according to the U.S. Environmental Protection Agency.

Which county has the lowest median Air Quality Index (US EPA)?

Eau Claire County, with 12 in 2005.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: median daily AQI. Retrieved 2026-10-12. 14 counties have no value for 2005 and are not ranked.

Median Air Quality Index (US EPA): other rankings

Counties in Wisconsin: more rankings