Data / Rankings / Share of days with good air quality (US EPA AQI) / US counties

US counties by share of days with good air quality (US EPA AQI)

Abbeville County had the highest share of days with good air quality (US EPA AQI) of 1006 counties in 2017, at 100%. San Bernardino County had the lowest, at 2.5%. The median was 75.2%. Source: EPA.

Keep it in a collection in your library.
Highest100Abbeville County
Lowest2.5San Bernardino County
Median75.21006 counties

Map of counties, 2017

%, 2017. Hatched areas have no value for this period. Source: Invokely calculation with data from EPA. Boundaries: U.S. Census Bureau cartographic boundary files.

Top 40 counties, 2017

Abbeville County: 100 %Abbeville County100Aleutians East Borough: 100 %Aleutians East Borough100Alexandria city: 100 %Alexandria city100Carroll County: 100 %Carroll County100Chaffee County: 100 %Chaffee County100Columbiana County: 100 %Columbiana County100Fredericksburg city: 100 %Fredericksburg city100Fremont County: 100 %Fremont County100Grady County: 100 %Grady County100Hopewell city: 100 %Hopewell city100Kenai Peninsula Borough: 100 %Kenai Peninsula Borough100Pitkin County: 100 %Pitkin County100San Juan County: 100 %San Juan County100Winchester city: 100 %Winchester city100Denali Borough: 99.7 %Denali Borough99.7Georgetown County: 99.7 %Georgetown County99.7Putnam County: 99.4 %Putnam County99.4Yalobusha County: 99.4 %Yalobusha County99.4Alamosa County: 99.2 %Alamosa County99.2Gilmer County: 99.2 %Gilmer County99.2Cerro Gordo County: 99.1 %Cerro Gordo County99.1Delta County: 99.1 %Delta County99.1Lincoln County: 99.1 %Lincoln County99.1Los Alamos County: 99.1 %Los Alamos County99.1Custer County: 99 %Custer County99Apache County: 98.9 %Apache County98.9Ford County: 98.9 %Ford County98.9Franklin County: 98.9 %Franklin County98.9Horry County: 98.9 %Horry County98.9Meade County: 98.9 %Meade County98.9Herkimer County: 98.7 %Herkimer County98.7Ashland County: 98.6 %Ashland County98.6Liberty County: 98.6 %Liberty County98.6Jackson County: 98.3 %Jackson County98.3Kauai County: 98.3 %Kauai County98.3Mohave County: 98.3 %Mohave County98.3Prowers County: 98.3 %Prowers County98.3Sherman County: 98.3 %Sherman County98.3Socorro County: 98.3 %Socorro County98.3Wayne County: 98.2 %Wayne County98.2Abbeville County: 100 %Abbeville County100Aleutians East Borough: 100 %Aleutians East Borough100Alexandria city: 100 %Alexandria city100Carroll County: 100 %Carroll County100Chaffee County: 100 %Chaffee County100Columbiana County: 100 %Columbiana County100Fredericksburg city: 100 %Fredericksburg city100Fremont County: 100 %Fremont County100Grady County: 100 %Grady County100Hopewell city: 100 %Hopewell city100Kenai Peninsula Borough: 100 %Kenai Peninsula Borough100Pitkin County: 100 %Pitkin County100San Juan County: 100 %San Juan County100Winchester city: 100 %Winchester city100Denali Borough: 99.7 %Denali Borough99.7Georgetown County: 99.7 %Georgetown County99.7Putnam County: 99.4 %Putnam County99.4Yalobusha County: 99.4 %Yalobusha County99.4Alamosa County: 99.2 %Alamosa County99.2Gilmer County: 99.2 %Gilmer County99.2Cerro Gordo County: 99.1 %Cerro Gordo County99.1Delta County: 99.1 %Delta County99.1Lincoln County: 99.1 %Lincoln County99.1Los Alamos County: 99.1 %Los Alamos County99.1Custer County: 99 %Custer County99Apache County: 98.9 %Apache County98.9Ford County: 98.9 %Ford County98.9Franklin County: 98.9 %Franklin County98.9Horry County: 98.9 %Horry County98.9Meade County: 98.9 %Meade County98.9Herkimer County: 98.7 %Herkimer County98.7Ashland County: 98.6 %Ashland County98.6Liberty County: 98.6 %Liberty County98.6Jackson County: 98.3 %Jackson County98.3Kauai County: 98.3 %Kauai County98.3Mohave County: 98.3 %Mohave County98.3Prowers County: 98.3 %Prowers County98.3Sherman County: 98.3 %Sherman County98.3Socorro County: 98.3 %Socorro County98.3Wayne County: 98.2 %Wayne County98.2
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2017 (%)Change on 2016
1Abbeville County100+8.4 pts
1Aleutians East Borough100+1.7 pts
1Alexandria city100+3.3 pts
1Carroll County1000 pts
1Chaffee County100+35.8 pts
1Columbiana County1000 pts
1Fredericksburg city1000 pts
1Fremont County1000 pts
1Grady County1000 pts
1Hopewell city1000 pts
1Kenai Peninsula Borough1000 pts
1Pitkin County1000 pts
1San Juan County1000 pts
1Winchester city1000 pts
15Denali Borough99.70 pts
15Georgetown County99.7+0.7 pts
17Putnam County99.4-0.6 pts
17Yalobusha County99.4+1.3 pts
19Alamosa County99.2+0.9 pts
19Gilmer County99.2+2.7 pts
21Cerro Gordo County99.1+0.2 pts
21Delta County99.1+0.8 pts
21Lincoln County99.1+2.6 pts
21Los Alamos County99.1-0.9 pts
25Custer County99-0.2 pts
26Apache County98.90 pts
26Ford County98.9+0.5 pts
26Franklin County98.9+2.5 pts
26Horry County98.9-1.1 pts
26Meade County98.9+2.2 pts
31Herkimer County98.7+1.6 pts
32Ashland County98.6+3.1 pts
32Liberty County98.6+1.2 pts
34Jackson County98.3-0.8 pts
34Kauai County98.30 pts
34Mohave County98.3+4.7 pts
34Prowers County98.3+0.3 pts
34Sherman County98.3+15.5 pts
34Socorro County98.3-0.7 pts
40Wayne County98.2-1.8 pts
41Muskogee County98.1-0.5 pts
41Stutsman County98.1-0.3 pts
43Lauderdale County98+2.2 pts
44Elmore County97.8+6.3 pts
45Franklin County97.7-2 pts
45Prince Edward County97.7+1.7 pts
47Windham County97.5+0.3 pts
48Polk County97.4-1.2 pts
48Routt County97.40 pts
50Greenup County97.3+5.5 pts
51Fauquier County97.1+4.6 pts
52Luzerne County97+5.2 pts
52Washington County97-1.4 pts
54Carteret County96.8+2.6 pts
55Chattooga County96.7+7 pts
55Lake County96.7-0.8 pts
55Merrimack County96.7+0.6 pts
58Stafford County96.6+12.7 pts
59Catron County96.5+0.2 pts
59Macon County96.5+3.5 pts
61Caddo County96.4-1.4 pts
61Clark County96.4-2.5 pts
61Lee County96.4+2.3 pts
64Aiken County96.3+6.6 pts
64Hughes County96.3-0.6 pts
64Mille Lacs County96.3-0.4 pts
64Saratoga County96.3+2.6 pts
68Anderson County96.2+2.4 pts
68Morgan County96.2+12 pts
70DeKalb County96.1+2.1 pts
70Flagler County96.1+0.5 pts
70Oswego County96.1+3.9 pts
73Tompkins County96+4.3 pts
74Columbia County95.9+6.6 pts
74Keweenaw County95.9-2.4 pts
76Middlesex County95.8+1.6 pts
77Sheridan County95.6-1 pts
77St. James Parish95.6+0.8 pts
79Baker County95.5+2.2 pts
79Highlands County95.5-0.1 pts
81Tucker County95.4+3.8 pts
82Elk County95.3+2.5 pts
82Hamilton County95.3-0.1 pts
82Knox County95.3+0.8 pts
82Lincoln County95.3-3.9 pts
86Dutchess County95.2+3.4 pts
87Greenbrier County95+3.7 pts
87Kennebec County95+0.8 pts
87Monmouth County95+8.6 pts
87Osceola County95+1.6 pts
87Sumter County95+6 pts
92Choctaw County94.8n/a
92Jefferson County94.8+2.3 pts
92Nye County94.8-0.6 pts
92Thomas County94.8-4.3 pts
96Hyde County94.7+4.9 pts
96Martin County94.7+0.8 pts
98Cook County94.6-2.6 pts
99Big Horn County94.5-3.4 pts
99Caswell County94.5+2.4 pts
99Okaloosa County94.50 pts
99Pointe Coupee Parish94.5-0.3 pts
99Trigg County94.5+5.1 pts
104Berkeley County94.4-0.5 pts
104Luna County94.4+0.5 pts
104Roosevelt County94.4-1.8 pts
104Wexford County94.4+1.7 pts
108Goodhue County94.3-0.1 pts
108Wythe County94.3+2.5 pts
110Claiborne County94.2+0.9 pts
110Leavenworth County94.2+2.2 pts
110Lycoming County94.2+2.7 pts
110Monroe County94.2-2.2 pts
110Scioto County94.2+6.5 pts
110Somerset County94.2+3.4 pts
110Tuscola County94.2+2 pts
117Lincoln County94.1+11.6 pts
117Marathon County94.1+2.4 pts
117Morgan County94.1+3.4 pts
117Putnam County94.1+5.1 pts
117St. Lucie County94.1+0.2 pts
122Bolivar County94+3 pts
122Culberson County94-4.2 pts
122Hunt County94-1.9 pts
125Wayne County93.8+2.3 pts
126Dukes County93.6-1 pts
127Jo Daviess County93.5-1.1 pts
128Adams County93.4+0.8 pts
128Giles County93.4+1.9 pts
130Boone County93.3+5.3 pts
130Chaves County93.3-3.3 pts
130Victoria County93.3-1 pts
133Cherokee County93.2+0.3 pts
133Grand County93.2+7 pts
133Honolulu County93.2+3 pts
133Manatee County93.2-0.5 pts
133Rowan County93.2+6.3 pts
133Taos County93.2-3.2 pts
139Caroline County93.1+5.2 pts
139Delaware County93.1+8.7 pts
139Gregg County93.1+1.3 pts
139St. John the Baptist Parish93.1-2 pts
139Suffolk city93.1+2.4 pts
144Bremer County92.9+0.9 pts
144Huron County92.9+3.8 pts
144Shelby County92.9+8.9 pts
144Steuben County92.9+4.5 pts
148Alexander County92.8+4.3 pts
148Simpson County92.8+3.5 pts
150Barnstable County92.7+0.4 pts
150Darlington County92.7+1.4 pts
150Huntington County92.7+6 pts
153Callaway County92.6-0.9 pts
153Dawson County92.6+4.1 pts
153Newton County92.6+0.5 pts
153Norfolk County92.6+3.3 pts
153Rockbridge County92.6+2.1 pts
158Wilson County92.4+9.7 pts
159Norfolk city92.3-2.7 pts
159Smith County92.3-1.7 pts
161Jessamine County92.2+6.9 pts
161Pike County92.2+6.7 pts
161Potter County92.2-3.4 pts
161Rockwall County92.2+0.3 pts
161Vilas County92.20 pts
166Hillsborough County92.1+3.6 pts
167Ascension Parish92-0.3 pts
167Niagara County92+2.5 pts
169Cass County91.8+0.3 pts
169Lake County91.8+2.3 pts
169Lenoir County91.8+3.2 pts
172Hendricks County91.7+11.9 pts
172Washington County91.7+0.9 pts
174Carter County91.6+3.1 pts
174Clearfield County91.6+1.4 pts
174Mayes County91.6+1.8 pts
174St. Martin Parish91.6+1.8 pts
174Williamson County91.6+1.8 pts
179Carlton County91.5-1.1 pts
179Fond du Lac County91.5+4.2 pts
179Prince William County91.5+3.2 pts
179Trego County91.5+0.2 pts
183Elko County91.4-7.2 pts
184Fayette County91.3+3.5 pts
184Montrose County91.3-2 pts
186Belmont County91.2+3.8 pts
186Jackson County91.2+11.4 pts
186Maui County91.2+2.7 pts
189Manitowoc County91.1+6 pts
189Pickens County91.1+8.9 pts
189York County91.1+1.7 pts
192Knox County91+3.8 pts
192Knox County91+8.8 pts
192Wabash County91+2 pts
195Lawrence County90.9-0.9 pts
195Paulding County90.9+48.9 pts
195Person County90.9+1.2 pts
198Avery County90.8+4.8 pts
198Hood County90.8-2.1 pts
198Parker County90.8-0.4 pts
201Indian River County90.7-2.2 pts
202Kitsap County90.6-6 pts
203Carroll County90.5+9.7 pts
203Indiana County90.5+3.2 pts
203Kent County90.5+3.8 pts
203Schoolcraft County90.5+1.9 pts
203Taney County90.5+1.1 pts
208Lake County90.4-4.4 pts
208Pueblo County90.4-4.1 pts
210Door County90.3+6.3 pts
210Hanover County90.3+6.2 pts
210Johnson County90.3+4 pts
210Livingston County90.3+5.3 pts
214Licking County90.2+9.8 pts
215Custer County90.1+1.3 pts
215Walworth County90.1+4.5 pts
217Lake County90-7.5 pts
217Platte County90+2.3 pts
219Jefferson County89.9-6.7 pts
219Knox County89.9-2.4 pts
221Forest County89.8-3.1 pts
222Pasco County89.7+0.1 pts
223York County89.6-1.2 pts
224Blaine County89.5+3.7 pts
225Boone County89.4+10.4 pts
225Boone County89.4-3.1 pts
225Washington County89.4+1.1 pts
228Bullitt County89.3+3.7 pts
228Macoupin County89.3-0.4 pts
230Ward County89.2n/a
231Bryan County89.1n/a
232Columbia County89+0.6 pts
232Hancock County89-0.1 pts
232Jasper County89+0.6 pts
232Skagit County89-1.4 pts
236Kewaunee County88.9+2.7 pts
236Weston County88.9+0.9 pts
238Brown County88.8-0.3 pts
238Rockingham County88.8+1.4 pts
240Clinton County88.7+9.7 pts
240Creek County88.7-1.4 pts
242Hancock County88.6+6 pts
242Mason County88.6+1.4 pts
242Wood County88.6+9.2 pts
245Adams County88.5-9.5 pts
245Becker County88.5-1.3 pts
245Benzie County88.5+2.6 pts
245Billings County88.5-7.9 pts
245Brown County88.5+1.1 pts
250Columbia County88.4-8.7 pts

Showing the top 250 of 1006. The Excel download has every row.

Other periods

About this ranking

Days with a daily Air Quality Index of 0 to 50 (good) as a percentage of the days of the year with an AQI in a US county. Calculated by Invokely from the day counts in the EPA AirData annual summaries; both counts are stored with each value.

United States counties with air quality monitors only, about 1,000 of some 3,100 in recent years; a county without monitors has no value. The number of days with an AQI differs between counties because some monitors run only in the ozone season.

Every value in the ranking comes from the same publisher and the same period, so the counties are compared on one definition. 492 counties with data in other periods have no value for 2017 and are left out rather than filled from another source. Equal values share a rank.

How to cite

U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.

Citation styles

The publisher is the author. Invokely is named only as the place the figures were read, where a style asks for it.

APA 7

U.S. Environmental Protection Agency. (2026). EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts (US counties by share of days with good air quality (US EPA AQI), 2017) [Data set]. Retrieved October 12, 2026, from https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual

MLA 9

EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, US counties by share of days with good air quality (US EPA AQI), 2017. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/good-air-quality-days-share/us-counties?period=2017. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. US counties by share of days with good air quality (US EPA AQI), 2017. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/good-air-quality-days-share/us-counties?period=2017.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts, US counties by share of days with good air quality (US EPA AQI), 2017 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/good-air-quality-days-share/us-counties?period=2017 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_us_counties_by_share_2017,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: US counties by share of days with good air quality (US EPA AQI), 2017}},
  year = {2026},
  howpublished = {Data set},
  url = {https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual},
  urldate = {2026-10-12},
  note = {Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/us-counties?period=2017. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download\_files.html\#Annual. Retrieved 2026-10-12.},
}
RIS
TY  - DATA
AU  - U.S. Environmental Protection Agency
TI  - EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts: US counties by share of days with good air quality (US EPA AQI), 2017
PY  - 2026
DA  - 2026/07/13
PB  - U.S. Environmental Protection Agency
DB  - Invokely
UR  - https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual
L2  - https://invokely.ai/rankings/good-air-quality-days-share/us-counties?period=2017
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/us-counties?period=2017.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Retrieved 2026-10-12.
ER  -
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Questions

Which county has the highest share of days with good air quality (US EPA AQI)?

Abbeville County, with 100% in 2017, according to EPA.

Which county has the lowest share of days with good air quality (US EPA AQI)?

San Bernardino County, with 2.5% in 2017.

Where does this ranking come from?

Every value comes from one source and one period, so the places are comparable: U.S. Environmental Protection Agency, EPA AirData annual AQI by county: good days as a share of days with an AQI, calculated with stored counts. Retrieved 2026-10-12. 492 counties have no value for 2017 and are not ranked.

Share of days with good air quality (US EPA AQI): other rankings

US counties: more rankings