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 2017, at 94.2%. St. Louis County had the lowest, at 44.1%. The median was 80.3%. Source: EPA.

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Highest94.2Monroe County
Lowest44.1St. Louis County
Median80.321 counties

Map of counties, 2017

Andrew County: 83.5 %Boone County: 89.4 %Buchanan County: 55.9 %Callaway County: 92.6 %Cass County: 70.5 %Cedar County: 72.2 %Clay County: 68.1 %Clinton County: 80.8 %Greene County: 66.6 %Jackson County: 47.4 %Jasper County: 89 %Jefferson County: 63.3 %Lincoln County: 86.1 %Monroe County: 94.2 %Perry County: 82.4 %St. Charles County: 75.5 %Ste. Genevieve County: 83.3 %St. Louis County: 44.1 %Stoddard County: 80.3 %Taney County: 90.5 %St. Louis city: 45.2 %
  • Under 63
  • 63 to 72
  • 72 to 82
  • 82 to 89
  • 89 and over
  • No data
%, 2017. 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, 2017

Monroe County: 94.2 %Monroe County94.2Callaway County: 92.6 %Callaway County92.6Taney County: 90.5 %Taney County90.5Boone County: 89.4 %Boone County89.4Jasper County: 89 %Jasper County89Lincoln County: 86.1 %Lincoln County86.1Andrew County: 83.5 %Andrew County83.5Ste. Genevieve County: 83.3 %Ste. Genevieve County83.3Perry County: 82.4 %Perry County82.4Clinton County: 80.8 %Clinton County80.8Stoddard County: 80.3 %Stoddard County80.3St. Charles County: 75.5 %St. Charles County75.5Cedar County: 72.2 %Cedar County72.2Cass County: 70.5 %Cass County70.5Clay County: 68.1 %Clay County68.1Greene County: 66.6 %Greene County66.6Jefferson County: 63.3 %Jefferson County63.3Buchanan County: 55.9 %Buchanan County55.9Jackson County: 47.4 %Jackson County47.4St. Louis city: 45.2 %St. Louis city45.2St. Louis County: 44.1 %St. Louis County44.1Monroe County: 94.2 %Monroe County94.2Callaway County: 92.6 %Callaway County92.6Taney County: 90.5 %Taney County90.5Boone County: 89.4 %Boone County89.4Jasper County: 89 %Jasper County89Lincoln County: 86.1 %Lincoln County86.1Andrew County: 83.5 %Andrew County83.5Ste. Genevieve County: 83.3 %Ste. Genevieve County83.3Perry County: 82.4 %Perry County82.4Clinton County: 80.8 %Clinton County80.8Stoddard County: 80.3 %Stoddard County80.3St. Charles County: 75.5 %St. Charles County75.5Cedar County: 72.2 %Cedar County72.2Cass County: 70.5 %Cass County70.5Clay County: 68.1 %Clay County68.1Greene County: 66.6 %Greene County66.6Jefferson County: 63.3 %Jefferson County63.3Buchanan County: 55.9 %Buchanan County55.9Jackson County: 47.4 %Jackson County47.4St. Louis city: 45.2 %St. Louis city45.2St. Louis County: 44.1 %St. Louis County44.1
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2017 (%)Change on 2016
1Monroe County94.2-2.2 pts
2Callaway County92.6-0.9 pts
3Taney County90.5+1.1 pts
4Boone County89.4-3.1 pts
5Jasper County89+0.6 pts
6Lincoln County86.1+1.1 pts
7Andrew County83.5-4.4 pts
8Ste. Genevieve County83.3-3.1 pts
9Perry County82.4+1.6 pts
10Clinton County80.8-1.4 pts
11Stoddard County80.3+1.8 pts
12St. Charles County75.5+3.5 pts
13Cedar County72.2-4.9 pts
14Cass County70.5-10.3 pts
15Clay County68.1-7.5 pts
16Greene County66.6-5 pts
17Jefferson County63.3+3.5 pts
18Buchanan County55.9-7.2 pts
19Jackson County47.4-10.8 pts
20St. Louis city45.2+6.9 pts
21St. Louis County44.1-11.9 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 2017 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), 2017) [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), 2017. 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=2017. 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), 2017. 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=2017.

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), 2017 [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=2017 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_missouri_by_2017,
  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), 2017}},
  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=2017. 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), 2017
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=2017
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/missouri-counties?period=2017.
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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Rank Counties in Missouri by share of days with good air quality (US EPA AQI) using official data, and cite the source.
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Questions

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

Monroe County, with 94.2% in 2017, according to EPA.

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

St. Louis County, with 44.1% in 2017.

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 2017 and are not ranked.

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

Counties in Missouri: more rankings