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

Johnson County had the highest share of days with good air quality (US EPA AQI) of 19 counties in 2015, at 98.2%. Campbell County had the lowest, at 66%. The median was 87.1%. Source: EPA.

Highest98.2Johnson County

Lowest66Campbell County

Median87.119 counties

Map of counties, 2015

Under 78
78 to 85
85 to 88
88 to 92
92 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

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

Full ranking

Rank	Counties	2015 (%)	Change on 2014
1	Johnson County	98.2	+0.8 pts
2	Lincoln County	97.3	-0.8 pts
3	Platte County	95	-1.7 pts
4	Park County	93.7	+1.1 pts
5	Natrona County	90.1	+0.5 pts
6	Carbon County	89.3	-0.3 pts
7	Weston County	89	-1.4 pts
8	Teton County	88.2	+1.4 pts
9	Big Horn County	87.7	+0.8 pts
10	Sheridan County	87.1	-5 pts
11	Uinta County	86.6	-4.1 pts
12	Goshen County	85	-6.4 pts
13	Laramie County	82.7	+4.9 pts
14	Converse County	78.9	-5.5 pts
14	Sublette County	78.9	+4.4 pts
16	Albany County	75.9	-0.8 pts
17	Fremont County	75.6	-4.9 pts
18	Sweetwater County	70.1	+2.4 pts
19	Campbell County	66	-3.3 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. 2 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 Wyoming 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 Wyoming 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/wyoming-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 Wyoming 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/wyoming-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 Wyoming 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/wyoming-counties?period=2015 (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_wyoming_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 Wyoming 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/wyoming-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 Wyoming 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/wyoming-counties?period=2015
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/wyoming-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)?

Johnson County, with 98.2% in 2015, according to EPA.

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

Campbell County, with 66% 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. 2 counties have no value for 2015 and are not ranked.