National rankings · 2024

Air Quality Rankings

The cleanest and most-polluted U.S. counties, metros, and states, ranked from EPA Air Quality System monitoring data.

50
Counties ranked
53
States ranked

The national picture

The cleanest air in the country sits in Lawrence County, Alabama (100.0% Good days); the most polluted in Harris County, Texas (8.8%). Across 977 monitored counties the spread, not the average, is the real story.

100.0%
cleanest · Lawrence Co.
8.8%
most polluted · Harris Co.
76.5%
national avg Good days
Virgin Islands
cleanest state · 100.0%

Widest state gap: Virgin Islands (100.0% avg Good) vs Arizona (61.2%).

The 10 most polluted U.S. counties

Ranked by median Air Quality Index, the typical day's AQI across the year (higher is worse)

  1. 1 San Bernardino, California 90
  2. 2 Riverside, California 87
  3. 3 Los Angeles, California 77
  4. 4 El Paso, Texas 74
  5. 5 Maricopa, Arizona 71
  6. 6 Dona Ana, New Mexico 70
  7. 7 Pinal, Arizona 66
  8. 8 Clark, Nevada 64
  9. 9 Imperial, California 64
  10. 10 Harris, Texas 63

Median AQI · EPA Air Quality System (AQS), 2024

Cleanest countiesTop 50 by good-day share. Most polluted countiesTop 50 by median AQI. Cleanest metro areasMetros by good-day share. Most improved countiesBiggest good-day-share gain.

Top 25 Cleanest Counties

# County State Good % Median AQI
1 Lawrence Alabama 100.0% 23
2 Denali Alaska 100.0% 38
3 Kenai Peninsula Alaska 100.0% 8
4 North Slope Alaska 100.0% 7
5 Lake California 100.0% 17
6 Marin California 100.0% 21
7 Siskiyou California 100.0% 6
8 Sonoma California 100.0% 9
9 Jackson Colorado 100.0% 3
10 San Juan Colorado 100.0% 4
11 Custer Idaho 100.0% 3
12 Keweenaw Michigan 100.0% 7
13 Cook Minnesota 100.0% 12
14 Stoddard Missouri 100.0% 21
15 Taney Missouri 100.0% 26
16 Beaverhead Montana 100.0% 12
17 Lake Montana 100.0% 4
18 Powell Montana 100.0% 6
19 Roosevelt Montana 100.0% 9
20 Rosebud Montana 100.0% 4
21 Sanders Montana 100.0% 15
22 Sheridan Montana 100.0% 13
23 Catron New Mexico 100.0% 8
24 Los Alamos New Mexico 100.0% 10
25 Socorro New Mexico 100.0% 12

Top 25 Most Polluted Counties

# County State Good % Max AQI
1 Harris Texas 8.8% 172
2 Riverside California 10.6% 365
3 Los Angeles California 10.9% 201
4 San Bernardino California 12.4% 207
5 El Paso Texas 12.7% 2122
6 Maricopa Arizona 16.4% 366
7 Dona Ana New Mexico 19.4% 528
8 Bernalillo New Mexico 23.7% 228
9 Kern California 23.8% 143
10 Pinal Arizona 24.6% 1215
11 Clark Nevada 25.6% 138
12 Imperial California 27.4% 190
13 Tulare California 29.7% 140
14 Santa Barbara California 29.8% 186
15 Montgomery Texas 30.7% 133
16 Tarrant Texas 31.5% 162
17 Cameron Texas 31.7% 139
18 Hamilton Ohio 32.1% 154
19 Pulaski Arkansas 32.9% 239
20 Butler Ohio 33.3% 151
21 Nueces Texas 35.0% 137
22 Hidalgo Texas 36.2% 140
23 Jefferson Alabama 36.8% 112
24 Pima Arizona 37.0% 357
25 Salt Lake Utah 37.0% 175

Top 25 Cleanest Metro Areas

# Metro Area Good % Median AQI
1 Branson, MO 100.0% 26
2 Clearlake, CA 100.0% 17
3 Evanston, WY 100.0% 10
4 Guayama, PR 100.0% 18
5 Houghton, MI 100.0% 7
6 Los Alamos, NM 100.0% 10
7 Salem, OH 100.0% 12
8 San Francisco-Oakland-Hayward, CA 100.0% 21
9 Santa Rosa, CA 100.0% 9
10 Show Low, AZ 99.6% 12
11 Hailey, ID 99.4% 22
12 Moscow, ID 99.3% 24
13 Bozeman, MT 99.1% 14
14 Vallejo-Fairfield, CA 98.9% 34
15 Taos, NM 98.5% 14
16 Olympia-Tumwater, WA 98.1% 26
17 Aberdeen, WA 97.9% 19
18 Arkadelphia, AR 97.5% 35
19 Rockland, ME 97.3% 34
20 Twin Falls, ID 97.2% 24
21 Mount Vernon-Anacortes, WA 97.1% 22
22 Mayaguez, PR 96.9% 12
23 Kinston, NC 96.7% 37
24 Bellingham, WA 96.6% 30
25 Bremerton-Silverdale, WA 96.2% 21

All States Ranked by Air Quality

# State Avg Good % Avg AQI
1 Virgin Islands 100.0% 18
2 Hawaii 90.8% 28
3 Montana 90.6% 23
4 Alaska 89.1% 20
5 Puerto Rico 88.4% 21
6 Vermont 88.2% 32
7 Washington 87.9% 27
8 Minnesota 87.8% 33
9 Maine 86.8% 36
10 Virginia 86.1% 36
11 Idaho 85.1% 30
12 New Hampshire 84.6% 38
13 Kentucky 83.9% 40
14 Nebraska 83.6% 31
15 Wyoming 83.3% 32
16 Oregon 82.8% 29
17 Maryland 82.4% 41
18 Missouri 82.2% 40
19 North Carolina 82.0% 40
20 New York 81.5% 38
21 Michigan 81.1% 37
22 South Dakota 80.7% 36
23 Wisconsin 80.5% 39
24 Tennessee 80.3% 39
25 Massachusetts 78.8% 40
26 West Virginia 78.7% 39
27 Rhode Island 78.5% 39
28 North Dakota 77.7% 40
29 Alabama 77.2% 40
30 Kansas 77.1% 38
31 Connecticut 76.4% 42
32 New Jersey 76.4% 41
33 Florida 75.1% 41
34 Louisiana 74.5% 41
35 Nevada 73.6% 40
36 Pennsylvania 73.5% 40
37 Mississippi 72.6% 43
38 New Mexico 72.2% 35
39 South Carolina 71.6% 44
40 Indiana 71.0% 42
41 Illinois 70.5% 43
42 Delaware 70.1% 44
43 Colorado 69.8% 39
44 Georgia 68.7% 43
45 Ohio 68.6% 44
46 Oklahoma 68.6% 44
47 District of Columbia 68.1% 45
48 Iowa 67.4% 43
49 Arkansas 66.9% 45
50 Utah 65.4% 42
51 Texas 64.9% 42
52 California 64.3% 45
53 Arizona 61.2% 44

Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), 2024 U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), 2024

How to read these rankings

A ranking tells you where to start looking, not whether a place is safe to live.

  • Rankings here are sorted by Good-day share (the % of monitored days with AQI 0–50), so the top of a list is genuinely the cleanest air, not just the most data. Methodology
  • Monitor coverage varies: a county with few stations is described by a thinner sample, so compare like with like before concluding. Understand AQI
  • Looking for one place? Jump to its county or state profile for the full distribution, primary pollutant, and five-year trend. All counties

All rankings recompute directly from EPA AQS annual summaries (2020–2025) - no editorial curation, no advertiser influence. Found an error? The contact page has our correction process.

How These Air-Quality Rankings Are Compiled

Every ranking on this page is computed directly from the EPA Air Quality System (AQS) annual summary files, not editorially curated, and not influenced by advertisers. Counties and metros are ordered by the share of monitored days that fell in the "Good" band (AQI 0–50); states are ordered by the average of their counties' Good-day shares. The underlying numbers, Good %, median AQI, max AQI, monitored days, are visible on every county, metro, and state page so you can verify them. We recompute the rankings whenever EPA publishes a new annual release, and we document that cadence on the methodology page.

What These Rankings Mean (and What They Do Not)

Good-day share is a useful lens for comparing places, but it has limits. It reflects only the days a county's monitors actually reported, so a lightly monitored county is described by a thinner sample than one blanketed with stations. It also says nothing about which pollutant drove the bad days, ozone in summer behaves very differently from wildfire PM2.5, so a county near the bottom of one list may be perfectly fine for most of the year outside a short smoke season. Where a single year's wildfire activity skews a county, the five-year trend on its profile page tells the fuller story.

Why We Publish These Rankings

Air-quality data is published by the EPA as enormous annual CSV files that few people can read directly. Most visitors arrive with a concrete question - "where is the cleanest air?", "how does my county compare?", "which cities have the worst smog?" - and benefit from seeing a ranked, linked list backed by the official numbers. Publishing ranked views of public environmental data is long-established civic-data practice; we surface the raw figures, link to the EPA source, and avoid editorial spin. If a ranking ever reads as a value judgment the data does not support, email us via the contact page and we will review the wording.

Methodology, Sources, and Corrections

Every ranking is derived from the EPA AQS annual summaries linked on the methodology page. We do not blend proprietary signals and we do not substitute editor opinion for the data. If you believe a figure is miscomputed or a county is misclassified, contact us with the specific county or metro and the expected correction, and we will investigate against the source files. Corrections that affect a published ranking are rolled forward immediately; minor formatting fixes go out with the next scheduled refresh.

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.