South Dakota: 66 counties covered
Of 66 rated South Dakota counties, 48 are in EPA's highest radon-potential zone (Zone 1) — but every county page links to testing guidance regardless of zone, because a county rating is a county-wide average, not a reading for any one house.
- Minnehaha County
- Pennington County
- Lincoln County
- Brown County
- Brookings County
- Meade County
- Codington County
- Lawrence County
- Yankton County
- Davison County
- Beadle County
- Hughes County
- Union County
- Clay County
- Oglala Lakota County
- Lake County
- Butte County
- Roberts County
- Charles Mix County
- Custer County
- Todd County
- Turner County
- Grant County
- Hutchinson County
- Fall River County
- Bon Homme County
- Hamlin County
- Moody County
- Spink County
- McCook County
- Tripp County
- Day County
- Dewey County
- Walworth County
- Brule County
- Kingsbury County
- Marshall County
- Deuel County
- Gregory County
- Edmunds County
- Clark County
- Corson County
- Lyman County
- Hanson County
- Bennett County
- Hand County
- Stanley County
- Douglas County
- Perkins County
- Aurora County
- Jackson County
- Ziebach County
- Potter County
- Sanborn County
- McPherson County
- Miner County
- Faulk County
- Haakon County
- Mellette County
- Buffalo County
- Jerauld County
- Sully County
- Campbell County
- Harding County
- Hyde County
- Jones County