# Counties in North Dakota by share of days with good air quality (US EPA AQI), 2001

All 12 values come from U.S. Environmental Protection Agency for 2001, so the places are comparable. 3 counties have no value for that period and are not ranked.

- Indicator id: `aqi_good_days_share`
- Unit: %
- Definition: 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.
- Source: 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 (https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual)
- Retrieved: 2026-10-12
- Citation: 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.
- Web page: https://invokely.ai/rankings/good-air-quality-days-share/north-dakota-counties

| Rank | Place | % |
|---:|---|---:|
| 1 | McLean County | 100 |
| 2 | Oliver County | 97.8 |
| 3 | McKenzie County | 96.8 |
| 4 | Burke County | 96.2 |
| 5 | Dunn County | 95.9 |
| 6 | Mercer County | 95.1 |
| 7 | Billings County | 94.5 |
| 8 | Stark County | 87.1 |
| 9 | Steele County | 83 |
| 10 | Cass County | 82.5 |
| 11 | Burleigh County | 79.3 |
| 12 | Grand Forks County | 66.7 |