Data / Rankings / Share of days with good air quality (US EPA AQI) / Counties in Missouri

Counties in Missouri by share of days with good air quality (US EPA AQI)

Monroe County had the highest share of days with good air quality (US EPA AQI) of 21 counties in 2015, at 97.3%. St. Louis city had the lowest, at 33.4%. The median was 78%. Source: EPA.

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Highest97.3Monroe County
Lowest33.4St. Louis city
Median7821 counties

Map of counties, 2015

Andrew County: 86.4 %Boone County: 92.1 %Buchanan County: 49.2 %Callaway County: 86.9 %Cass County: 61.3 %Cedar County: 70.2 %Clay County: 59.9 %Clinton County: 78 %Greene County: 65.4 %Jackson County: 54.8 %Jasper County: 84.1 %Jefferson County: 38.9 %Lincoln County: 87.9 %Monroe County: 97.3 %Perry County: 83.2 %St. Charles County: 81.3 %Ste. Genevieve County: 86.4 %St. Louis County: 47.1 %Stoddard County: 73.1 %Taney County: 89.7 %St. Louis city: 33.4 %
  • Under 55
  • 55 to 70
  • 70 to 83
  • 83 to 87
  • 87 and over
  • No data
%, 2015. Hatched areas have no value for this period. Source: Invokely calculation with data from EPA. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2015

Monroe County: 97.3 %Monroe County97.3Boone County: 92.1 %Boone County92.1Taney County: 89.7 %Taney County89.7Lincoln County: 87.9 %Lincoln County87.9Callaway County: 86.9 %Callaway County86.9Andrew County: 86.4 %Andrew County86.4Ste. Genevieve County: 86.4 %Ste. Genevieve County86.4Jasper County: 84.1 %Jasper County84.1Perry County: 83.2 %Perry County83.2St. Charles County: 81.3 %St. Charles County81.3Clinton County: 78 %Clinton County78Stoddard County: 73.1 %Stoddard County73.1Cedar County: 70.2 %Cedar County70.2Greene County: 65.4 %Greene County65.4Cass County: 61.3 %Cass County61.3Clay County: 59.9 %Clay County59.9Jackson County: 54.8 %Jackson County54.8Buchanan County: 49.2 %Buchanan County49.2St. Louis County: 47.1 %St. Louis County47.1Jefferson County: 38.9 %Jefferson County38.9St. Louis city: 33.4 %St. Louis city33.4Monroe County: 97.3 %Monroe County97.3Boone County: 92.1 %Boone County92.1Taney County: 89.7 %Taney County89.7Lincoln County: 87.9 %Lincoln County87.9Callaway County: 86.9 %Callaway County86.9Andrew County: 86.4 %Andrew County86.4Ste. Genevieve County: 86.4 %Ste. Genevieve County86.4Jasper County: 84.1 %Jasper County84.1Perry County: 83.2 %Perry County83.2St. Charles County: 81.3 %St. Charles County81.3Clinton County: 78 %Clinton County78Stoddard County: 73.1 %Stoddard County73.1Cedar County: 70.2 %Cedar County70.2Greene County: 65.4 %Greene County65.4Cass County: 61.3 %Cass County61.3Clay County: 59.9 %Clay County59.9Jackson County: 54.8 %Jackson County54.8Buchanan County: 49.2 %Buchanan County49.2St. Louis County: 47.1 %St. Louis County47.1Jefferson County: 38.9 %Jefferson County38.9St. Louis city: 33.4 %St. Louis city33.4
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2015 (%)Change on 2014
1Monroe County97.3+2.8 pts
2Boone County92.1+3.3 pts
3Taney County89.7+2.6 pts
4Lincoln County87.9+4.3 pts
5Callaway County86.9-3.2 pts
6Andrew County86.4+0.6 pts
6Ste. Genevieve County86.4+23.4 pts
8Jasper County84.1+5.5 pts
9Perry County83.2+1 pts
10St. Charles County81.3+3.7 pts
11Clinton County78-5.9 pts
12Stoddard County73.1+8.9 pts
13Cedar County70.2+7.3 pts
14Greene County65.4+8.4 pts
15Cass County61.3+18.2 pts
16Clay County59.9+4 pts
17Jackson County54.8+2.7 pts
18Buchanan County49.2+5.9 pts
19St. Louis County47.1-4.1 pts
20Jefferson County38.9-8.5 pts
21St. Louis city33.4+3 pts

Other periods

About this ranking

Days with a daily Air Quality Index of 0 to 50 (good) as a percentage of the days of the year with an AQI in a US county. Calculated by Invokely from the day counts in the EPA AirData annual summaries; both counts are stored with each value.

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. 13 counties with data in other periods have no value for 2015 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: good days as a share of days with an AQI, calculated with stored counts. 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: good days as a share of days with an AQI, calculated with stored counts (Counties in Missouri by share of days with good air quality (US EPA AQI), 2015) [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: good days as a share of days with an AQI, calculated with stored counts, Counties in Missouri by share of days with good air quality (US EPA AQI), 2015. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/good-air-quality-days-share/missouri-counties?period=2015. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. Counties in Missouri by share of days with good air quality (US EPA AQI), 2015. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/good-air-quality-days-share/missouri-counties?period=2015.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, Counties in Missouri by share of days with good air quality (US EPA AQI), 2015 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/missouri-counties?period=2015 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_missouri_by_2015,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: Counties in Missouri by share of days with good air quality (US EPA AQI), 2015}},
  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/good-air-quality-days-share/missouri-counties?period=2015. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. 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: good days as a share of days with an AQI, calculated with stored counts: Counties in Missouri by share of days with good air quality (US EPA AQI), 2015
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/good-air-quality-days-share/missouri-counties?period=2015
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/missouri-counties?period=2015.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. 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 share of days with good air quality (US EPA AQI)?

Monroe County, with 97.3% in 2015, according to EPA.

Which county has the lowest share of days with good air quality (US EPA AQI)?

St. Louis city, with 33.4% in 2015.

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: good days as a share of days with an AQI, calculated with stored counts. Retrieved 2026-10-12. 13 counties have no value for 2015 and are not ranked.

Share of days with good air quality (US EPA AQI): other rankings

Counties in Missouri: more rankings