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

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

Gilmer County had the highest share of days with good air quality (US EPA AQI) of 17 counties in 2001, at 83.4%. Marion County had the lowest, at 21.8%. The median was 41.7%. Source: EPA.

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Highest83.4Gilmer County
Lowest21.8Marion County
Median41.717 counties

Map of counties, 2001

Berkeley County: 41.7 %Brooke County: 65.8 %Cabell County: 41.6 %Gilmer County: 83.4 %Greenbrier County: 53.5 %Hancock County: 51.5 %Harrison County: 24.2 %Kanawha County: 37.9 %Marion County: 21.8 %Marshall County: 23.1 %Mercer County: 38.8 %Monongalia County: 44.6 %Ohio County: 57.8 %Raleigh County: 29.8 %Summers County: 55.3 %Tucker County: 72.3 %Wood County: 39.2 %
  • Under 31
  • 31 to 40
  • 40 to 49
  • 49 to 57
  • 57 and over
  • No data
%, 2001. 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, 2001

Gilmer County: 83.4 %Gilmer County83.4Tucker County: 72.3 %Tucker County72.3Brooke County: 65.8 %Brooke County65.8Ohio County: 57.8 %Ohio County57.8Summers County: 55.3 %Summers County55.3Greenbrier County: 53.5 %Greenbrier County53.5Hancock County: 51.5 %Hancock County51.5Monongalia County: 44.6 %Monongalia County44.6Berkeley County: 41.7 %Berkeley County41.7Cabell County: 41.6 %Cabell County41.6Wood County: 39.2 %Wood County39.2Mercer County: 38.8 %Mercer County38.8Kanawha County: 37.9 %Kanawha County37.9Raleigh County: 29.8 %Raleigh County29.8Harrison County: 24.2 %Harrison County24.2Marshall County: 23.1 %Marshall County23.1Marion County: 21.8 %Marion County21.8Gilmer County: 83.4 %Gilmer County83.4Tucker County: 72.3 %Tucker County72.3Brooke County: 65.8 %Brooke County65.8Ohio County: 57.8 %Ohio County57.8Summers County: 55.3 %Summers County55.3Greenbrier County: 53.5 %Greenbrier County53.5Hancock County: 51.5 %Hancock County51.5Monongalia County: 44.6 %Monongalia County44.6Berkeley County: 41.7 %Berkeley County41.7Cabell County: 41.6 %Cabell County41.6Wood County: 39.2 %Wood County39.2Mercer County: 38.8 %Mercer County38.8Kanawha County: 37.9 %Kanawha County37.9Raleigh County: 29.8 %Raleigh County29.8Harrison County: 24.2 %Harrison County24.2Marshall County: 23.1 %Marshall County23.1Marion County: 21.8 %Marion County21.8
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2001 (%)Change on 2000
1Gilmer County83.4+0.1 pts
2Tucker County72.3+3.9 pts
3Brooke County65.8-3.3 pts
4Ohio County57.8-12.1 pts
5Summers County55.3-2.3 pts
6Greenbrier County53.5-2.9 pts
7Hancock County51.5-8.3 pts
8Monongalia County44.6-3.8 pts
9Berkeley County41.7+16.9 pts
10Cabell County41.6-0.4 pts
11Wood County39.2-3.9 pts
12Mercer County38.8+12.9 pts
13Kanawha County37.9-2.5 pts
14Raleigh County29.8+0.6 pts
15Harrison County24.2-2.8 pts
16Marshall County23.1+0.1 pts
17Marion County21.8-4.6 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. 3 counties with data in other periods have no value for 2001 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 West Virginia by share of days with good air quality (US EPA AQI), 2001) [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 West Virginia by share of days with good air quality (US EPA AQI), 2001. 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/west-virginia-counties?period=2001. 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 West Virginia by share of days with good air quality (US EPA AQI), 2001. 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/west-virginia-counties?period=2001.

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 West Virginia by share of days with good air quality (US EPA AQI), 2001 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/west-virginia-counties?period=2001 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_west_virginia_2001,
  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 West Virginia by share of days with good air quality (US EPA AQI), 2001}},
  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/west-virginia-counties?period=2001. 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 West Virginia by share of days with good air quality (US EPA AQI), 2001
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/west-virginia-counties?period=2001
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/west-virginia-counties?period=2001.
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)?

Gilmer County, with 83.4% in 2001, according to EPA.

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

Marion County, with 21.8% in 2001.

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. 3 counties have no value for 2001 and are not ranked.

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

Counties in West Virginia: more rankings