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), 995 monitored counties and 501 metro areas reported Air Quality Index readings through the federal Air Quality System (AQS) for the 2024 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% 8 Good
2 North Slope County, Alaska 100.0% 5 Good
3 Thomas County, Nebraska 100.0% 12 Good
4 Los Alamos County, New Mexico 100.0% 14 Good
5 Socorro County, New Mexico 100.0% 16 Good
6 Columbiana County, Ohio 100.0% 12 Good
7 Lawrence County, Pennsylvania 100.0% 24 Good
8 Mayagnez County, Puerto Rico 100.0% 11 Good
9 Karnes County, Texas 100.0% 7 Good
10 Wilson County, Texas 100.0% 7 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% 7 Good
15 Routt County, Colorado 99.7% 12 Good
16 Maui County, Hawaii 99.7% 21 Good
17 Pacific County, Washington 99.7% 16 Good
18 Martin County, North Carolina 99.7% 31 Good
19 Lauderdale County, Mississippi 99.6% 36 Good
20 Navajo County, Arizona 99.5% 13 Good
21 Lake County, California 99.5% 32 Good
22 Apache County, Arizona 99.4% 14 Good
23 San Juan County, Colorado 99.2% 9 Good
24 Aleutians East County, Alaska 99.1% 13 Good
25 Liberty County, Florida 99.1% 31 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.