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 2014, at 94.5%. St. Louis city had the lowest, at 30.4%. The median was 64.2%. Source: EPA.

Highest94.5Monroe County

Lowest30.4St. Louis city

Median64.221 counties

Map of counties, 2014

Under 51
51 to 63
63 to 79
79 to 86
86 and over
No data

%, 2014. 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, 2014

%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2014 (%)	Change on 2013
1	Monroe County	94.5	+2.5 pts
2	Callaway County	90.1	+2.2 pts
3	Boone County	88.8	+5.6 pts
4	Taney County	87.1	+5.7 pts
5	Andrew County	85.8	+3.6 pts
6	Clinton County	83.9	+6.8 pts
7	Lincoln County	83.6	+7.9 pts
8	Perry County	82.2	-1 pts
9	Jasper County	78.6	-5.1 pts
10	St. Charles County	77.6	+6.6 pts
11	Stoddard County	64.2	+4.4 pts
12	Ste. Genevieve County	63	-3.9 pts
13	Cedar County	62.9	+4.5 pts
14	Greene County	57	-3.6 pts
15	Clay County	55.9	+1.8 pts
16	Jackson County	52.1	+6.1 pts
17	St. Louis County	51.2	+14.2 pts
18	Jefferson County	47.4	-0.8 pts
19	Buchanan County	43.3	+4.3 pts
20	Cass County	43.1	-12.6 pts
21	St. Louis city	30.4	+0.8 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 2014 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), 2014) [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), 2014. 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=2014. 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), 2014. 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=2014.

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), 2014 [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=2014 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_missouri_by_2014,
  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), 2014}},
  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=2014. 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), 2014
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=2014
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/missouri-counties?period=2014.
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 94.5% in 2014, according to EPA.

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

St. Louis city, with 30.4% in 2014.

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 2014 and are not ranked.