Data / Rankings / Share of days with good air quality (US EPA AQI) / Counties in Maryland

Counties in Maryland by share of days with good air quality (US EPA AQI)

Calvert County had the highest share of days with good air quality (US EPA AQI) of 16 counties in 2017, at 82.9%. Kent County had the lowest, at 54.2%. The median was 68.8%. Source: EPA.

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Highest82.9Calvert County
Lowest54.2Kent County
Median68.816 counties

Map of counties, 2017

Anne Arundel County: 81.5 %Baltimore County: 71.8 %Calvert County: 82.9 %Carroll County: 82 %Cecil County: 61.7 %Charles County: 78.4 %Dorchester County: 58.1 %Frederick County: 78.2 %Garrett County: 78.3 %Harford County: 57.5 %Howard County: 64.1 %Kent County: 54.2 %Montgomery County: 74.7 %Prince George's County: 65.8 %Washington County: 61.9 %Baltimore city: 60.5 %
  • Under 61
  • 61 to 64
  • 64 to 75
  • 75 to 78
  • 78 and over
  • No data
%, 2017. Hatched areas have no value for this period. Source: Invokely calculation with data from EPA. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2017

Calvert County: 82.9 %Calvert County82.9Carroll County: 82 %Carroll County82Anne Arundel County: 81.5 %Anne Arundel County81.5Charles County: 78.4 %Charles County78.4Garrett County: 78.3 %Garrett County78.3Frederick County: 78.2 %Frederick County78.2Montgomery County: 74.7 %Montgomery County74.7Baltimore County: 71.8 %Baltimore County71.8Prince George's County: 65.8 %Prince George's County65.8Howard County: 64.1 %Howard County64.1Washington County: 61.9 %Washington County61.9Cecil County: 61.7 %Cecil County61.7Baltimore city: 60.5 %Baltimore city60.5Dorchester County: 58.1 %Dorchester County58.1Harford County: 57.5 %Harford County57.5Kent County: 54.2 %Kent County54.2Calvert County: 82.9 %Calvert County82.9Carroll County: 82 %Carroll County82Anne Arundel County: 81.5 %Anne Arundel County81.5Charles County: 78.4 %Charles County78.4Garrett County: 78.3 %Garrett County78.3Frederick County: 78.2 %Frederick County78.2Montgomery County: 74.7 %Montgomery County74.7Baltimore County: 71.8 %Baltimore County71.8Prince George's County: 65.8 %Prince George's County65.8Howard County: 64.1 %Howard County64.1Washington County: 61.9 %Washington County61.9Cecil County: 61.7 %Cecil County61.7Baltimore city: 60.5 %Baltimore city60.5Dorchester County: 58.1 %Dorchester County58.1Harford County: 57.5 %Harford County57.5Kent County: 54.2 %Kent County54.2
%. Source: Invokely calculation with data from EPA. Retrieved 2026-10-12.

Full ranking

RankCounties2017 (%)Change on 2016
1Calvert County82.9+5.8 pts
2Carroll County82+3.2 pts
3Anne Arundel County81.5+19.3 pts
4Charles County78.4+0.5 pts
5Garrett County78.3-4.4 pts
6Frederick County78.2+6.6 pts
7Montgomery County74.7+2.8 pts
8Baltimore County71.8+17.2 pts
9Prince George's County65.8+11.4 pts
10Howard County64.1+11.1 pts
11Washington County61.9+2.4 pts
12Cecil County61.7+3.5 pts
13Baltimore city60.5+8 pts
14Dorchester County58.1-6.4 pts
15Harford County57.5-1.3 pts
16Kent County54.2-18.3 pts

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. 3 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 (Counties in Maryland 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, Counties in Maryland 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/maryland-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. Counties in Maryland 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/maryland-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, Counties in Maryland 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/maryland-counties?period=2017 (Accessed: 12 October 2026).

BibTeX
@misc{environmental_counties_in_maryland_by_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: Counties in Maryland 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/maryland-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: Counties in Maryland 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/maryland-counties?period=2017
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/good-air-quality-days-share/maryland-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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Rank Counties in Maryland by share of days with good air quality (US EPA AQI) using official data, and cite the source.
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Questions

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

Calvert County, with 82.9% in 2017, according to EPA.

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

Kent County, with 54.2% 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. 3 counties have no value for 2017 and are not ranked.

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

Counties in Maryland: more rankings