National ranking · cleanest air

50 Counties with the Best Air Quality

Ranked by the highest share of Good air days among counties with at least 100 monitored days in the year, the counties where residents breathe the cleanest air most often, from EPA Air Quality System monitoring.

100.0%
#1 Denali, Alaska
50
Counties ranked

Counties below the 100-day monitoring floor are excluded: with only a handful of readings, a single clean stretch can push a county to a 100% Good-day rate that a normal year's weather would not hold up. 9 counties tie at 100.0% with this floor applied, all with a genuinely large sample of monitored days. For comparison, the cohort median across all 896 floor-qualifying counties is 78.4%, meaning the difference between a top-ranked county and a typical monitored county is real, not sampling noise.

Cleanest of the clean: lowest median AQI

Among the top counties (all near a 100% Good-day record), the lowest typical AQI. Shorter is cleaner.

  1. 1 Karnes, Texas 4
  2. 2 Wilson, Texas 7
  3. 3 Carbon, Wyoming 7
  4. 4 Sonoma, California 9
  5. 5 Washakie, Wyoming 10
  6. 6 Lincoln, Wyoming 10
  7. 7 Beaverhead, Montana 12
  8. 8 Navajo, Arizona 12
  9. 9 Apache, Arizona 14
  10. 10 Park, Wyoming 14
  11. 11 Gallatin, Montana 14
  12. 12 Taos, New Mexico 14

Median AQI · EPA Air Quality System

# County State Good Days % Median AQI
1 Denali Alaska 100.0% 38 Good
2 Sonoma California 100.0% 9 Good
3 Beaverhead Montana 100.0% 12 Good
4 Sanders Montana 100.0% 15 Good
5 Martin North Carolina 100.0% 28 Good
6 Karnes Texas 100.0% 4 Good
7 Wilson Texas 100.0% 7 Good
8 Pacific Washington 100.0% 15 Good
9 Carbon Wyoming 100.0% 7 Good
10 Apache Arizona 99.6% 14 Good
11 Navajo Arizona 99.6% 12 Good
12 Park Wyoming 99.5% 14 Good
13 Blaine Idaho 99.4% 22 Good
14 Latah Idaho 99.3% 24 Good
15 Gallatin Montana 99.1% 14 Good
16 Solano California 98.9% 34 Good
17 Taos New Mexico 98.5% 14 Good
18 Thurston Washington 98.1% 26 Good
19 Washakie Wyoming 98.0% 10 Good
20 Grays Harbor Washington 97.9% 19 Good
21 Lincoln Wyoming 97.8% 10 Good
22 Liberty Florida 97.7% 32 Good
23 Teton Montana 97.7% 14 Good
24 Clark Arkansas 97.5% 35 Good
25 Flagler Florida 97.4% 34 Good
26 Knox Maine 97.3% 34 Good
27 Twin Falls Idaho 97.2% 24 Good
28 Fauquier Virginia 97.2% 36 Good
29 Elmore Alabama 97.2% 32 Good
30 Skagit Washington 97.1% 22 Good
31 Oswego New York 97.0% 35 Good
32 Mayagnez Puerto Rico 96.9% 12 Good
33 Prince Edward Virginia 96.8% 35 Good
34 Lenoir North Carolina 96.7% 37 Good
35 Columbia Oregon 96.7% 25 Good
36 Morgan Kentucky 96.6% 35 Good
37 Hamilton New York 96.6% 36 Good
38 Whatcom Washington 96.6% 30 Good
39 Rockbridge Virginia 96.5% 35 Good
40 Cass Nebraska 96.5% 20 Good
41 Jefferson Washington 96.5% 19 Good
42 Glacier Montana 96.4% 22 Good
43 Claiborne Tennessee 96.3% 36 Good
44 Hanover Virginia 96.3% 37 Good
45 Suffolk City Virginia 96.3% 39 Good
46 Caroline Virginia 96.2% 37 Good
47 Caldwell North Carolina 96.2% 37 Good
48 Kitsap Washington 96.2% 21 Good
49 Maui Hawaii 96.1% 22 Good
50 Yalobusha Mississippi 96.1% 33 Good

Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS). Good Days % is the share of monitored days with AQI at or below 50. Counties ranked by good_pct descending U.S. Environmental Protection Agency (EPA), Air Quality System (AQS). Good Days % is the share of monitored days with AQI at or below 50. Counties ranked by good_pct descending

Every figure on PlainAir is rendered directly from EPA AQS air-quality monitoring data, no number is typed in by an editor. This page draws directly on EPA AQS air-quality monitoring data, no figure is typed in by an editor. See our editorial standards & corrections policy, the methodology behind these numbers, or report a data error.