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RankingsMontanaHighest radon potential

Counties with the Highest Radon Potential in Montana

The top 25 of 56 Montana counties on GIS Map, ranked by EPA radon zone, where zone 1 carries the highest predicted indoor radon potential and zone 3 the lowest.

#CountyEPA radon zone
1Golden Valley County
2
2Musselshell County
2
3Petroleum County
2
4Sweet Grass County
2
5Treasure County
2
6Wheatland County
2
7Yellowstone County
2
8Beaverhead County
1
9Big Horn County
1
10Blaine County
1
11Broadwater County
1
12Carbon County
1
13Carter County
1
14Cascade County
1
15Chouteau County
1
16Custer County
1
17Daniels County
1
18Dawson County
1
19Deer Lodge County
1
20Fallon County
1
21Fergus County
1
22Flathead County
1
23Gallatin County
1
24Garfield County
1
25Glacier County
1

Source: EPA Map of Radon Zones (September 2025). All counties with data are ranked. Estimates carry margins of error.

Citing this page: GIS Map, “Counties with the Highest Radon Potential in Montana”, https://gismap.land/rankings/montana/highest-radon-counties. Figures from EPA Map of Radon Zones (September 2025).

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