Counties in North Dakota by share of days with good air quality (US EPA AQI), 2001
McLean County had the highest share of days with good air quality (US EPA AQI) of 12 counties in 2001, at 100%. Grand Forks County had the lowest, at 66.7%. The median was 94.8%. Source: EPA.
Map of counties, 2001
- Under 83
- 83 to 90
- 90 to 96
- 96 to 97
- 97 and over
- No data
All counties, 2001
Full ranking
| Rank | Counties | 2001 (%) | Change on 2000 |
|---|---|---|---|
| 1 | McLean County | 100 | 0 pts |
| 2 | Oliver County | 97.8 | -0.6 pts |
| 3 | McKenzie County | 96.8 | -3.2 pts |
| 4 | Burke County | 96.2 | +1.4 pts |
| 5 | Dunn County | 95.9 | -4.1 pts |
| 6 | Mercer County | 95.1 | -1.6 pts |
| 7 | Billings County | 94.5 | +1.1 pts |
| 8 | Stark County | 87.1 | -7.8 pts |
| 9 | Steele County | 83 | -11 pts |
| 10 | Cass County | 82.5 | -5.2 pts |
| 11 | Burleigh County | 79.3 | +1.9 pts |
| 12 | Grand Forks County | 66.7 | -5 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
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 North Dakota 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 North Dakota 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/north-dakota-counties. 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 North Dakota 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/north-dakota-counties.
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 North Dakota 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/north-dakota-counties (Accessed: 12 October 2026).
BibTeX
@misc{environmental_counties_in_north_dakota_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 North Dakota 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/north-dakota-counties. 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 North Dakota 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/north-dakota-counties
Y2 - 2026/10/12
N1 - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/north-dakota-counties.
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 -
Use this data in your AI agent
Invokely serves this figure to AI assistants through MCP and to code through a REST API, with the source and citation attached. Ask your assistant:
Rank Counties in North Dakota by share of days with good air quality (US EPA AQI) using official data, and cite the source.
rank_places {"indicator":"aqi_good_days_share","level":"province","within":"North Dakota","limit":10}
GET https://invokely.ai/api/v1/rank?indicator=aqi_good_days_share&level=province&within=North%20Dakota&limit=10Questions
Which county has the highest share of days with good air quality (US EPA AQI)?
McLean County, with 100% in 2001, according to EPA.
Which county has the lowest share of days with good air quality (US EPA AQI)?
Grand Forks County, with 66.7% 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.