Updated April 2026 · EPA Air Quality System

Cleanest Air Cities in America

The 200 U.S. cities with the cleanest air, ranked by Air Quality Grade across 10 years of EPA monitoring data. The top 50 average a 5-year median AQI of 19 — about 51% below the national city-level average of 39.

What "Cleanest" Means Here

Every city in this ranking is graded on the same four signals: 5-year median AQI (40% of the composite), 10-year trend direction (30%), unhealthy-day count per year (20%), and which pollutant dominates the local air (10%). Together these answer not just "is the air clean today" but "is it reliably clean year-round, and is it getting better." A city that scrapes a low average through one calm year but trends worsening still loses points; a city that runs a stable 35 AQI for a decade earns the top tier.

All numbers come from the EPA's AirNow network and Air Quality System Annual AQI by County data, processed into per-city profiles. No estimates, no proxies — every reading is a federally certified monitor measurement.

Top 10 Quick Look

#	City	5-yr Median AQI	Grade	Trend
1	Caguas, Puerto Rico	10	A	Improving
2	Alexandria City, Virginia	6	A	Improving
3	Cook, Minnesota	12	A	Improving
4	San Juan, Puerto Rico	10	A	Improving
5	Carbon, Wyoming	16	A	Improving
6	Monroe, Michigan	21	A	Improving
7	Juncos, Puerto Rico	9	A	Improving
8	Matanuska-Susitna, Alaska	17	A	Improving
9	Uinta, Wyoming	21	A	Improving
10	Adjuntas, Puerto Rico	19	A	Improving

Common Patterns at the Top

The cities that consistently rank in the cleanest tier share a few structural features: low population density (fewer vehicle and combustion sources), prevailing wind patterns that move pollution away rather than concentrate it, and distance from major freight corridors and heavy industry. Coastal towns benefit from regular onshore winds; high-elevation Mountain West communities often see clean readings simply because there's less to pollute.

What's notable is how few large metros appear in the top tier. Most U.S. cities of 500K+ population struggle to break into A territory because vehicle emissions, urban heat-island ozone formation, and warehouse/freight clusters compound. The cleanest large-metro readings tend to come from Pacific Northwest cities outside wildfire seasons.

Full Ranking — Top 200 Cleanest Cities

#1Caguas, Puerto Rico

Median AQI: 65yr Avg: 10↓ Improving

Primary pollutant: NO2

#2Alexandria City, Virginia

Median AQI: 65yr Avg: 6↓ Improving

Primary pollutant: PM10

#3Cook, Minnesota

Median AQI: 135yr Avg: 12↓ Improving

Primary pollutant: PM2.5

#4San Juan, Puerto Rico

Median AQI: 75yr Avg: 10↓ Improving

Primary pollutant: CO

#5Carbon, Wyoming

Median AQI: 85yr Avg: 16↓ Improving

Primary pollutant: Ozone

#6Monroe, Michigan

Median AQI: 255yr Avg: 21↓ Improving

Primary pollutant: PM10

#7Juncos, Puerto Rico

Median AQI: 95yr Avg: 9↓ Improving

Primary pollutant: Ozone

#8Matanuska-Susitna, Alaska

Median AQI: 145yr Avg: 17↓ Improving

Primary pollutant: PM2.5

#9Uinta, Wyoming

Median AQI: 65yr Avg: 21↓ Improving

Primary pollutant: Ozone

#10Adjuntas, Puerto Rico

Median AQI: 145yr Avg: 19↓ Improving

Primary pollutant: PM2.5

#11Hawaii, Hawaii

Median AQI: 235yr Avg: 25↓ Improving

Primary pollutant: PM2.5

#12Rosebud, Montana

Median AQI: 35yr Avg: 23↓ Improving

Primary pollutant: Ozone

#13Luna, New Mexico

Median AQI: 165yr Avg: 17↓ Improving

Primary pollutant: PM10

#14Bayamon, Puerto Rico

Median AQI: 225yr Avg: 18↓ Improving

Primary pollutant: CO

#15Colleton, South Carolina

Median AQI: 265yr Avg: 26↓ Improving

Primary pollutant: PM2.5

#16St Croix, Virgin Islands

Median AQI: 295yr Avg: 27↓ Improving

Primary pollutant: PM2.5

#17Hughes, South Dakota

Median AQI: 145yr Avg: 13↓ Improving

Primary pollutant: PM2.5

#18Humboldt, California

Median AQI: 325yr Avg: 28↓ Improving

Primary pollutant: Ozone

#19Hopewell City, Virginia

Median AQI: 75yr Avg: 7↓ Improving

Primary pollutant: PM10

#20Winchester City, Virginia

Median AQI: 65yr Avg: 7↓ Improving

Primary pollutant: PM10

#21Maui, Hawaii

Median AQI: 205yr Avg: 21↓ Improving

Primary pollutant: PM2.5

#22Cass, Nebraska

Median AQI: 175yr Avg: 16↓ Improving

Primary pollutant: PM10

#23Columbiana, Ohio

Median AQI: 115yr Avg: 12↓ Improving

Primary pollutant: PM10

#24Jefferson, Oregon

Median AQI: 315yr Avg: 28↓ Improving

Primary pollutant: PM2.5

#25Georgetown, South Carolina

Median AQI: 145yr Avg: 14↓ Improving

Primary pollutant: PM10

#26St John, Virgin Islands

Median AQI: 225yr Avg: 21↓ Improving

Primary pollutant: PM2.5

#27Carroll, Virginia

Median AQI: 95yr Avg: 8→ Stable

Primary pollutant: PM10

#28Wyoming, Pennsylvania

Median AQI: 275yr Avg: 33↓ Improving

Primary pollutant: PM2.5

#29Alamosa, Colorado

Median AQI: 225yr Avg: 14↓ Improving

Primary pollutant: PM10

#30Kauai, Hawaii

Median AQI: 135yr Avg: 15↓ Improving

Primary pollutant: PM2.5

#31Floyd, Indiana

Median AQI: 465yr Avg: 36↓ Improving

Primary pollutant: Ozone

#32Jackson, Indiana

Median AQI: 355yr Avg: 35↓ Improving

Primary pollutant: Ozone

#33Taney, Missouri

Median AQI: 295yr Avg: 26↓ Improving

Primary pollutant: PM2.5

#34Jackson, North Carolina

Median AQI: 385yr Avg: 35↓ Improving

Primary pollutant: Ozone

#35Muskogee, Oklahoma

Median AQI: 185yr Avg: 18↓ Improving

Primary pollutant: PM10

#36Windham, Vermont

Median AQI: 145yr Avg: 12↓ Improving

Primary pollutant: PM2.5

#37Anchorage, Alaska

Median AQI: 215yr Avg: 26↓ Improving

Primary pollutant: PM2.5

#38Fremont, Colorado

Median AQI: 125yr Avg: 13→ Stable

Primary pollutant: PM10

#39Morgan, Indiana

Median AQI: 355yr Avg: 35↓ Improving

Primary pollutant: Ozone

#40Douglas, Nevada

Median AQI: 285yr Avg: 22↓ Improving

Primary pollutant: PM2.5

#41Norfolk City, Virginia

Median AQI: 185yr Avg: 18↓ Improving

Primary pollutant: NO2

#42Garfield, Washington

Median AQI: 175yr Avg: 20↓ Improving

Primary pollutant: PM2.5

#43North Slope, Alaska

Median AQI: 45yr Avg: 6↓ Improving

Primary pollutant: PM2.5

#44Tuscaloosa, Alabama

Median AQI: 425yr Avg: 37↓ Improving

Primary pollutant: Ozone

#45Juneau, Alaska

Median AQI: 245yr Avg: 22↓ Improving

Primary pollutant: PM2.5

#46Apache, Arizona

Median AQI: 135yr Avg: 13→ Stable

Primary pollutant: PM10

#47Routt, Colorado

Median AQI: 135yr Avg: 14→ Stable

Primary pollutant: PM10

#48Custer, Idaho

Median AQI: 85yr Avg: 8→ Stable

Primary pollutant: PM2.5

#49Roane, Tennessee

Median AQI: 365yr Avg: 36↓ Improving

Primary pollutant: PM2.5

#50Custer, Oklahoma

Median AQI: 145yr Avg: 14→ Stable

Primary pollutant: PM10

#51Mohave, Arizona

Median AQI: 155yr Avg: 17→ Stable

Primary pollutant: PM10

#52Pitkin, Colorado

Median AQI: 135yr Avg: 13→ Stable

Primary pollutant: PM10

#53Wasco, Oregon

Median AQI: 275yr Avg: 24↓ Improving

Primary pollutant: PM2.5

#54Aleutians East, Alaska

Median AQI: 115yr Avg: 12→ Stable

Primary pollutant: PM2.5

#55Kenai Peninsula, Alaska

Median AQI: 105yr Avg: 10→ Stable

Primary pollutant: PM2.5

#56Napa, California

Median AQI: 415yr Avg: 39↓ Improving

Primary pollutant: PM2.5

#57San Juan, Colorado

Median AQI: 95yr Avg: 9→ Stable

Primary pollutant: PM2.5

#58Charlton, Georgia

Median AQI: 275yr Avg: 26↓ Improving

Primary pollutant: PM2.5

#59Floyd, Georgia

Median AQI: 465yr Avg: 43↓ Improving

Primary pollutant: PM2.5

#60Orleans, Louisiana

Median AQI: 415yr Avg: 36↓ Improving

Primary pollutant: PM2.5

#61Howard, Maryland

Median AQI: 385yr Avg: 37↓ Improving

Primary pollutant: PM2.5

#62Ravalli, Montana

Median AQI: 225yr Avg: 22↓ Improving

Primary pollutant: PM2.5

#63Roosevelt, Montana

Median AQI: 135yr Avg: 14→ Stable

Primary pollutant: PM2.5

#64Scotts Bluff, Nebraska

Median AQI: 215yr Avg: 24↓ Improving

Primary pollutant: PM2.5

#65Socorro, New Mexico

Median AQI: 145yr Avg: 15→ Stable

Primary pollutant: PM2.5

#66Hyde, North Carolina

Median AQI: 265yr Avg: 23↓ Improving

Primary pollutant: PM2.5

#67Martin, North Carolina

Median AQI: 365yr Avg: 35↓ Improving

Primary pollutant: Ozone

#68Mitchell, North Carolina

Median AQI: 335yr Avg: 30↓ Improving

Primary pollutant: PM2.5

#69Athens, Ohio

Median AQI: 315yr Avg: 30↓ Improving

Primary pollutant: PM2.5

#70Guayama, Puerto Rico

Median AQI: 155yr Avg: 24↓ Improving

Primary pollutant: PM2.5

#71Lubbock, Texas

Median AQI: 255yr Avg: 28↓ Improving

Primary pollutant: PM2.5

#72Cowlitz, Washington

Median AQI: 225yr Avg: 22↓ Improving

Primary pollutant: PM2.5

#73Skagit, Washington

Median AQI: 305yr Avg: 28↓ Improving

Primary pollutant: PM2.5

#74Jerome, Idaho

Median AQI: 135yr Avg: 17↓ Improving

Primary pollutant: PM2.5

#75Sherman, Kansas

Median AQI: 195yr Avg: 16→ Stable

Primary pollutant: PM10

#76Pike, Kentucky

Median AQI: 395yr Avg: 39↓ Improving

Primary pollutant: PM2.5

#77Bay, Michigan

Median AQI: 425yr Avg: 32↓ Improving

Primary pollutant: PM2.5

#78Keweenaw, Michigan

Median AQI: 165yr Avg: 13→ Stable

Primary pollutant: PM2.5

#79Winona, Minnesota

Median AQI: 285yr Avg: 23↓ Improving

Primary pollutant: PM2.5

#80Lake, Montana

Median AQI: 135yr Avg: 10→ Stable

Primary pollutant: PM2.5

#81Silver Bow, Montana

Median AQI: 315yr Avg: 27↓ Improving

Primary pollutant: PM2.5

#82Catron, New Mexico

Median AQI: 135yr Avg: 13→ Stable

Primary pollutant: PM2.5

#83Lincoln, New Mexico

Median AQI: 145yr Avg: 14→ Stable

Primary pollutant: PM2.5

#84Mercer, Pennsylvania

Median AQI: 445yr Avg: 42↓ Improving

Primary pollutant: Ozone

#85Monroe, Pennsylvania

Median AQI: 345yr Avg: 35↓ Improving

Primary pollutant: Ozone

#86Montgomery, Tennessee

Median AQI: 365yr Avg: 35↓ Improving

Primary pollutant: PM2.5

#87Wayne, Utah

Median AQI: 125yr Avg: 11→ Stable

Primary pollutant: PM2.5

#88Jefferson, Washington

Median AQI: 215yr Avg: 22↓ Improving

Primary pollutant: PM2.5

#89Marion, West Virginia

Median AQI: 395yr Avg: 38↓ Improving

Primary pollutant: PM2.5

#90Marin, California

Median AQI: 345yr Avg: 36↓ Improving

Primary pollutant: PM2.5

#91Putnam, Florida

Median AQI: 175yr Avg: 16↑ Worsening

Primary pollutant: PM10

#92Honolulu, Hawaii

Median AQI: 315yr Avg: 29↓ Improving

Primary pollutant: Ozone

#93Allen, Indiana

Median AQI: 425yr Avg: 42↓ Improving

Primary pollutant: PM2.5

#94Powell, Montana

Median AQI: 145yr Avg: 11→ Stable

Primary pollutant: PM2.5

#95Thomas, Nebraska

Median AQI: 175yr Avg: 17→ Stable

Primary pollutant: PM2.5

#96Los Alamos, New Mexico

Median AQI: 145yr Avg: 13→ Stable

Primary pollutant: PM2.5

#97Caswell, North Carolina

Median AQI: 365yr Avg: 37↓ Improving

Primary pollutant: Ozone

#98Union, Oregon

Median AQI: 265yr Avg: 27↓ Improving

Primary pollutant: PM2.5

#99Lynchburg City, Virginia

Median AQI: 345yr Avg: 31↓ Improving

Primary pollutant: PM2.5

#100Salem City, Virginia

Median AQI: 365yr Avg: 34↓ Improving

Primary pollutant: PM2.5

#101Adams, Washington

Median AQI: 215yr Avg: 18↓ Improving

Primary pollutant: PM2.5

#102Mason, Washington

Median AQI: 245yr Avg: 24↓ Improving

Primary pollutant: PM2.5

#103Thurston, Washington

Median AQI: 285yr Avg: 27↓ Improving

Primary pollutant: PM2.5

#104Twin Falls, Idaho

Median AQI: 255yr Avg: 27↓ Improving

Primary pollutant: PM2.5

#105Lawrence, Alabama

Median AQI: 345yr Avg: 29↓ Improving

Primary pollutant: PM2.5

#106Prowers, Colorado

Median AQI: 195yr Avg: 17→ Stable

Primary pollutant: PM10

#107Orange, Florida

Median AQI: 435yr Avg: 38↓ Improving

Primary pollutant: Ozone

#108Cobb, Georgia

Median AQI: 435yr Avg: 41↓ Improving

Primary pollutant: Ozone

#109Franklin, Idaho

Median AQI: 245yr Avg: 25↓ Improving

Primary pollutant: PM2.5

#110Carroll, Indiana

Median AQI: 365yr Avg: 34↓ Improving

Primary pollutant: Ozone

#111Posey, Indiana

Median AQI: 385yr Avg: 34↓ Improving

Primary pollutant: Ozone

#112Cerro Gordo, Iowa

Median AQI: 195yr Avg: 18↑ Worsening

Primary pollutant: PM10

#113Androscoggin, Maine

Median AQI: 355yr Avg: 34↓ Improving

Primary pollutant: PM2.5

#114Sheridan, Montana

Median AQI: 185yr Avg: 16→ Stable

Primary pollutant: PM2.5

#115Oneida, New York

Median AQI: 325yr Avg: 25↓ Improving

Primary pollutant: PM2.5

#116Clermont, Ohio

Median AQI: 415yr Avg: 42↓ Improving

Primary pollutant: PM2.5

#117Westmoreland, Pennsylvania

Median AQI: 425yr Avg: 42↓ Improving

Primary pollutant: PM2.5

#118Lawrence, Tennessee

Median AQI: 415yr Avg: 33↓ Improving

Primary pollutant: PM2.5

#119Maury, Tennessee

Median AQI: 365yr Avg: 33↓ Improving

Primary pollutant: PM2.5

#120Putnam, Tennessee

Median AQI: 385yr Avg: 34↓ Improving

Primary pollutant: PM2.5

#121Fayette, Texas

Median AQI: 345yr Avg: 34↓ Improving

Primary pollutant: PM2.5

#122Maverick, Texas

Median AQI: 345yr Avg: 35↓ Improving

Primary pollutant: PM2.5

#123Grays Harbor, Washington

Median AQI: 235yr Avg: 25↓ Improving

Primary pollutant: PM2.5

#124Lewis, Washington

Median AQI: 255yr Avg: 25↓ Improving

Primary pollutant: PM2.5

#125Brooke, West Virginia

Median AQI: 195yr Avg: 19→ Stable

Primary pollutant: PM10

#126Platte, Wyoming

Median AQI: 145yr Avg: 16→ Stable

Primary pollutant: PM10

#127Clay, Alabama

Median AQI: 415yr Avg: 37↓ Improving

Primary pollutant: PM2.5

#128Boone, Indiana

Median AQI: 375yr Avg: 35↓ Improving

Primary pollutant: Ozone

#129Huntington, Indiana

Median AQI: 315yr Avg: 31↓ Improving

Primary pollutant: Ozone

#130Perry, Indiana

Median AQI: 385yr Avg: 36↓ Improving

Primary pollutant: Ozone

#131Warrick, Indiana

Median AQI: 385yr Avg: 36↓ Improving

Primary pollutant: Ozone

#132Ford, Kansas

Median AQI: 155yr Avg: 15↑ Worsening

Primary pollutant: PM10

#133Aroostook, Maine

Median AQI: 375yr Avg: 36↓ Improving

Primary pollutant: PM2.5

#134Penobscot, Maine

Median AQI: 355yr Avg: 33↓ Improving

Primary pollutant: PM2.5

#135Prince George's, Maryland

Median AQI: 445yr Avg: 42↓ Improving

Primary pollutant: Ozone

#136Suffolk, Massachusetts

Median AQI: 445yr Avg: 44↓ Improving

Primary pollutant: PM2.5

#137Washington, Minnesota

Median AQI: 425yr Avg: 37↓ Improving

Primary pollutant: Ozone

#138Stoddard, Missouri

Median AQI: 375yr Avg: 31↓ Improving

Primary pollutant: PM2.5

#139Sarpy, Nebraska

Median AQI: 375yr Avg: 38↓ Improving

Primary pollutant: PM2.5

#140Washington, Nebraska

Median AQI: 335yr Avg: 31↓ Improving

Primary pollutant: PM2.5

#141Herkimer, New York

Median AQI: 295yr Avg: 29↓ Improving

Primary pollutant: Ozone

#142Deschutes, Oregon

Median AQI: 285yr Avg: 25↓ Improving

Primary pollutant: PM2.5

#143Bucks, Pennsylvania

Median AQI: 395yr Avg: 37↓ Improving

Primary pollutant: Ozone

#144Erie, Pennsylvania

Median AQI: 425yr Avg: 39↓ Improving

Primary pollutant: PM2.5

#145Oconee, South Carolina

Median AQI: 375yr Avg: 37↓ Improving

Primary pollutant: Ozone

#146Brown, South Dakota

Median AQI: 295yr Avg: 26↓ Improving

Primary pollutant: PM2.5

#147Bristol City, Virginia

Median AQI: 395yr Avg: 35↓ Improving

Primary pollutant: PM2.5

#148Harrison, West Virginia

Median AQI: 395yr Avg: 37↓ Improving

Primary pollutant: PM2.5

#149Park, Wyoming

Median AQI: 145yr Avg: 20→ Stable

Primary pollutant: PM2.5

#150Lake, California

Median AQI: 325yr Avg: 32↓ Improving

Primary pollutant: Ozone

#151Columbia, Georgia

Median AQI: 365yr Avg: 35↓ Improving

Primary pollutant: Ozone

#152Clark, Illinois

Median AQI: 365yr Avg: 34↓ Improving

Primary pollutant: Ozone

#153Macoupin, Illinois

Median AQI: 375yr Avg: 33↓ Improving

Primary pollutant: Ozone

#154Shelby, Indiana

Median AQI: 375yr Avg: 35↓ Improving

Primary pollutant: Ozone

#155Chase, Kansas

Median AQI: 295yr Avg: 26→ Stable

Primary pollutant: PM2.5

#156Rockingham, New Hampshire

Median AQI: 405yr Avg: 40↓ Improving

Primary pollutant: Ozone

#157Chaves, New Mexico

Median AQI: 245yr Avg: 24→ Stable

Primary pollutant: PM2.5

#158Nassau, New York

Median AQI: 315yr Avg: 30↓ Improving

Primary pollutant: PM2.5

#159Ellis, Texas

Median AQI: 365yr Avg: 41↓ Improving

Primary pollutant: PM2.5

#160Box Elder, Utah

Median AQI: 385yr Avg: 39↓ Improving

Primary pollutant: Ozone

#161Garfield, Utah

Median AQI: 105yr Avg: 36↓ Improving

Primary pollutant: Ozone

#162Stafford, Virginia

Median AQI: 375yr Avg: 36↓ Improving

Primary pollutant: Ozone

#163Franklin, Washington

Median AQI: 265yr Avg: 22→ Stable

Primary pollutant: PM2.5

#164Klickitat, Washington

Median AQI: 205yr Avg: 22→ Stable

Primary pollutant: PM2.5

#165Whatcom, Washington

Median AQI: 315yr Avg: 29↓ Improving

Primary pollutant: PM2.5

#166Belmont, Ohio

Median AQI: 315yr Avg: 18↑ Worsening

Primary pollutant: NO2

#167Northampton, North Carolina

Median AQI: 375yr Avg: 35↓ Improving

Primary pollutant: PM2.5

#168San Mateo, California

Median AQI: 315yr Avg: 36↓ Improving

Primary pollutant: PM2.5

#169Coffee, Georgia

Median AQI: 415yr Avg: 36↓ Improving

Primary pollutant: PM2.5

#170Brown, Indiana

Median AQI: 375yr Avg: 35↓ Improving

Primary pollutant: Ozone

#171Elkhart, Indiana

Median AQI: 445yr Avg: 43↓ Improving

Primary pollutant: PM2.5

#172Kent, Maryland

Median AQI: 415yr Avg: 40↓ Improving

Primary pollutant: Ozone

#173Carlton, Minnesota

Median AQI: 385yr Avg: 29→ Stable

Primary pollutant: Ozone

#174Orange, New York

Median AQI: 345yr Avg: 37↓ Improving

Primary pollutant: Ozone

#175Greene, Ohio

Median AQI: 445yr Avg: 41↓ Improving

Primary pollutant: PM2.5

#176Clearfield, Pennsylvania

Median AQI: 355yr Avg: 33↓ Improving

Primary pollutant: Ozone

#177Northampton, Pennsylvania

Median AQI: 465yr Avg: 44↓ Improving

Primary pollutant: PM2.5

#178Chesterfield, South Carolina

Median AQI: 425yr Avg: 39↓ Improving

Primary pollutant: PM2.5

#179Ector, Texas

Median AQI: 335yr Avg: 36↓ Improving

Primary pollutant: PM2.5

#180Potter, Texas

Median AQI: 265yr Avg: 28→ Stable

Primary pollutant: PM2.5

#181Rockwall, Texas

Median AQI: 345yr Avg: 33↓ Improving

Primary pollutant: Ozone

#182Whitman, Washington

Median AQI: 265yr Avg: 23→ Stable

Primary pollutant: PM2.5

#183Kootenai, Idaho

Median AQI: 325yr Avg: 30↓ Improving

Primary pollutant: PM2.5

#184Sumter, Alabama

Median AQI: 355yr Avg: 36↓ Improving

Primary pollutant: PM2.5

#185Amador, California

Median AQI: 365yr Avg: 37↓ Improving

Primary pollutant: Ozone

#186Sonoma, California

Median AQI: 335yr Avg: 36↓ Improving

Primary pollutant: Ozone

#187Jackson, Colorado

Median AQI: 455yr Avg: 21↑ Worsening

Primary pollutant: PM2.5

#188Hartford, Connecticut

Median AQI: 435yr Avg: 42↓ Improving

Primary pollutant: PM2.5

#189Indian River, Florida

Median AQI: 345yr Avg: 35↓ Improving

Primary pollutant: Ozone

#190Manatee, Florida

Median AQI: 355yr Avg: 34→ Stable

Primary pollutant: Ozone

#191Nassau, Florida

Median AQI: 425yr Avg: 42↓ Improving

Primary pollutant: PM2.5

#192Hendricks, Indiana

Median AQI: 375yr Avg: 34↓ Improving

Primary pollutant: Ozone

#193Howard, Indiana

Median AQI: 455yr Avg: 44↓ Improving

Primary pollutant: PM2.5

#194Hardin, Kentucky

Median AQI: 455yr Avg: 44↓ Improving

Primary pollutant: PM2.5

#195Ascension, Louisiana

Median AQI: 345yr Avg: 32→ Stable

Primary pollutant: Ozone

#196Rapides, Louisiana

Median AQI: 435yr Avg: 39↓ Improving

Primary pollutant: PM2.5

#197St. James, Louisiana

Median AQI: 335yr Avg: 30→ Stable

Primary pollutant: Ozone

#198Baltimore (City), Maryland

Median AQI: 445yr Avg: 43↓ Improving

Primary pollutant: PM2.5

#199Calvert, Maryland

Median AQI: 425yr Avg: 39↓ Improving

Primary pollutant: Ozone

#200Garrett, Maryland

Median AQI: 405yr Avg: 39↓ Improving

Primary pollutant: Ozone

Frequently Asked Questions

What makes a city the "cleanest" in this ranking?

Each city's Air Quality Grade combines four signals from a decade of EPA Air Quality System data: 5-year median AQI (40% of the score), 10-year trend direction (30%), the count of "Unhealthy for Sensitive Groups" days per year (20%), and the dominant pollutant type (10%). Cities at the top of this ranking are A-graded — they post low median AQI, few caution days, and either flat or improving trends. The top 50 cities in this list average a 5-year median AQI of 19, well below the national city-level average of 39.

Which states have the most cities with clean air?

Among the top 50 ranked cities, Puerto Rico leads with 5 entries. Hawaii, Vermont, Maine, North Dakota, and parts of the rural Midwest tend to dominate the cleanest-air lists in EPA data. The pattern reflects low population density, distance from major highway corridors, and limited heavy industry — three factors that drive most fine-particulate and ozone formation.

Is "clean air" the same in every cleanest-air city?

No — two cities can both earn an A while differing on which pollutants are lowest. A coastal city in the Pacific Northwest might score well on PM2.5 but show seasonal ozone spikes; a high-elevation Mountain West town might be the inverse. The pollutant breakdown on each city profile shows which contaminant drives that city's grade.

Are these rankings updated as new EPA data comes out?

Yes. Rankings are recomputed each time EPA publishes the Annual AQI by County dataset (typically once per year, covering the prior calendar year). The current ranking reflects data through April 2026. As wildfire smoke patterns and emission rules change, the leaderboard shifts year to year — especially for Western metros where smoke can swing a city's grade by a full letter.

How does air quality affect health?

Sustained low PM2.5 and ozone exposure correlates with measurably lower rates of asthma hospitalization, cardiovascular events, low birth weight, and pollution-attributable mortality. The American Lung Association and World Health Organization both publish dose-response evidence linking long-term PM2.5 reductions to extended life expectancy. For people with asthma, COPD, or pregnancy, choosing a city with low long-run AQI is one of the more impactful environmental health decisions available.

How These Ranks Are Calculated

For each city, we compute a 5-year median AQI and a 10-year trend slope from EPA AQS Annual AQI by County data. Those feed a composite Air Quality Grade — 40% median AQI, 30% trend, 20% unhealthy days, 10% dominant pollutant — that produces both a 0–100 score and an A–F letter. Rankings sort first by grade, then by composite score, with median AQI as a tiebreaker. Read the full methodology.

Worst Air Quality Cities →Fastest-Improving Cities →Compare Any Two Cities →

Source: U.S. EPA Air Quality System (AQS), Annual AQI by County 2014–present. Public domain.

Last updated 2026-04-06 · Ranking covers 200 cities.