Counties in Indiana by highest daily Air Quality Index (US EPA), 2015

Allen County had the highest highest daily Air Quality Index (US EPA) of 39 counties in 2015, at 176. Hendricks County had the lowest, at 61. The median was 101. Source: the U.S. Environmental Protection Agency.

Highest176Allen County

Lowest61Hendricks County

Median10139 counties

Map of counties, 2015

Under 81
81 to 92
92 to 100
100 to 120
120 to 130
130 and over
No data

index, 2015. Hatched areas have no value for this period. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Boundaries: U.S. Census Bureau cartographic boundary files.

All counties, 2015

index. Source: EPA, EPA AirData annual AQI by county: highest daily AQI. Retrieved 2026-10-12.

Full ranking

Rank	Counties	2015 index	Change on 2014
1	Allen County	176	+29
2	Porter County	168	+53
3	Clark County	164	+42
4	Marion County	159	-50
5	Lake County	151	-5
5	Vigo County	151	+17
7	St. Joseph County	134	+5
8	Vanderburgh County	133	+25
9	LaPorte County	126	0
9	Wabash County	126	+18
11	Elkhart County	124	-2
12	Bartholomew County	115	+7
12	Greene County	115	+27
12	Posey County	115	+15
12	Warrick County	115	+10
16	Perry County	112	+11
17	Floyd County	108	-11
18	Delaware County	105	-25
19	Brown County	101	+30
19	Howard County	101	+17
19	Jackson County	101	+8
22	Tippecanoe County	99	-29
23	Boone County	97	-11
23	Hancock County	97	+30
25	Hamilton County	93	-36
25	Knox County	93	+3
27	Johnson County	90	+19
28	Madison County	89	-52
28	Whitley County	89	-36
30	Carroll County	87	-21
31	Montgomery County	83	+3
32	Monroe County	82	-77
33	Morgan County	80	-17
34	Dubois County	79	-18
35	Spencer County	78	-18
36	Shelby County	77	-23
37	Henry County	75	-44
38	Huntington County	71	-9
39	Hendricks County	61	-16

Other periods

About this ranking

Highest daily Air Quality Index (AQI) value recorded in a US county during the year, from the EPA AirData annual summaries. Values above 500 are beyond the AQI scale and are published as EPA computes them.

A single day decides the value, so one wildfire or dust event can set it. Dust from the dry Owens Lake bed puts Inyo and Mono counties in California in the thousands. 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. 14 counties with data in other periods have no value for 2015 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: highest daily AQI. 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: highest daily AQI (Counties in Indiana by highest daily Air Quality Index (US EPA), 2015) [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: highest daily AQI, Counties in Indiana by highest daily Air Quality Index (US EPA), 2015. U.S. Environmental Protection Agency, 13 July 2026, https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/indiana-counties. Accessed 12 Oct. 2026.

Chicago (author-date)

U.S. Environmental Protection Agency. 2026. EPA AirData annual AQI by county: highest daily AQI. Counties in Indiana by highest daily Air Quality Index (US EPA), 2015. Dataset. Accessed October 12, 2026. https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual. Also distributed by Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/indiana-counties.

Harvard

U.S. Environmental Protection Agency (2026) EPA AirData annual AQI by county: highest daily AQI, Counties in Indiana by highest daily Air Quality Index (US EPA), 2015 [Dataset]. Available at: https://aqs.epa.gov/aqsweb/airdata/download_files.html#Annual, via Invokely: https://invokely.ai/rankings/highest-daily-air-quality-index/indiana-counties (Accessed: 12 October 2026).

BibTeX

@misc{environmental_counties_in_indiana_by_2015,
  author = {{U.S. Environmental Protection Agency}},
  title = {{EPA AirData annual AQI by county: highest daily AQI: Counties in Indiana by highest daily Air Quality Index (US EPA), 2015}},
  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/highest-daily-air-quality-index/indiana-counties. Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. 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: highest daily AQI: Counties in Indiana by highest daily Air Quality Index (US EPA), 2015
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/highest-daily-air-quality-index/indiana-counties
Y2  - 2026/10/12
N1  - Accessed via Invokely, https://invokely.ai/rankings/highest-daily-air-quality-index/indiana-counties.
N1  - Publisher attribution: U.S. Environmental Protection Agency, Air Quality System, AirData. EPA AirData annual AQI by county: highest daily AQI. 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 highest daily Air Quality Index (US EPA)?

Allen County, with 176 in 2015, according to the U.S. Environmental Protection Agency.

Which county has the lowest highest daily Air Quality Index (US EPA)?

Hendricks County, with 61 in 2015.

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: highest daily AQI. Retrieved 2026-10-12. 14 counties have no value for 2015 and are not ranked.