Air quality tool

Cleanest Counties Finder

Filter U.S. counties by state and rank them by their share of Good air days, then open any county for the full picture.

According to the U.S. Environmental Protection Agency (EPA), 1002 monitored counties and 504 metro areas reported Air Quality Index readings through the federal Air Quality System (AQS) for the 2025 reporting year. This tool reads those official records directly; see the methodology for how every figure is computed.

Cleanest counties nationwide (25)

# County Good days Median AQI Category
1 Kenai Peninsula County, Alaska 100.0% 9 Good
2 Sonoma County, California 100.0% 9 Good
3 Keweenaw County, Michigan 100.0% 8 Good
4 Stoddard County, Missouri 100.0% 21 Good
5 Los Alamos County, New Mexico 100.0% 13 Good
6 Martin County, North Carolina 100.0% 31 Good
7 Columbiana County, Ohio 100.0% 12 Good
8 Lawrence County, Pennsylvania 100.0% 24 Good
9 Karnes County, Texas 100.0% 6 Good
10 Wilson County, Texas 100.0% 8 Good
11 Carroll County, Virginia 100.0% 7 Good
12 Hopewell City County, Virginia 100.0% 6 Good
13 Carbon County, Wyoming 100.0% 8 Good
14 Uinta County, Wyoming 100.0% 9 Good
15 Pacific County, Washington 99.7% 16 Good
16 Denali County, Alaska 99.7% 33 Good
17 Navajo County, Arizona 99.5% 13 Good
18 Lake County, California 99.2% 31 Good
19 Solano County, California 99.2% 33 Good
20 Aleutians East County, Alaska 99.0% 11 Good
21 San Juan County, Colorado 98.9% 12 Good
22 Lincoln County, Wyoming 98.9% 10 Good
23 Jackson County, Colorado 98.9% 9 Good
24 Taos County, New Mexico 98.9% 16 Good
25 Liberty County, Florida 98.5% 33 Good

More ways to explore

AQI lookupSearch a single county’s air quality. Compare countiesPut counties side by side. AQI health calculatorWhat an AQI value means for health. Cleanest-air rankingsNational good-day rankings. Browse by stateState summaries and county lists. MethodologyHow good-day share is built.

Frequently asked questions

How does the cleanest counties finder work?
Choose a state, or leave it on all states, and the tool ranks the matching counties by their share of Good air days from EPA Air Quality System data. Switch the order to surface either the cleanest or the most polluted counties. Each result links to a full county profile.
What is a Good air day?
A Good day is any monitored day with an Air Quality Index of 50 or below, the cleanest band on the EPA scale. Ranking by the share of Good days lets a heavily monitored county and a lightly monitored one compare fairly, because it is a percentage rather than a raw count.
Why might my state show only a few counties?
The EPA places monitors where population, emissions, or attainment status warrant them, so rural states can have only a handful of monitored counties. The finder ranks exactly the counties with an active monitor; unmonitored counties are not estimated.

Source: U.S. EPA Air Quality System (AQS) Annual AQI by county summary files · 2020–2025

Every figure on PlainAirData 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. Data current as of 2025.

Informational only, not professional advice. Data from EPA AQS. See our disclaimer.