Missouri: 115 counties covered
Of 115 rated Missouri counties, 11 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.
- St. Louis County
- Jackson County
- St. Charles County
- Greene County
- St. Louis city
- Clay County
- Jefferson County
- Boone County
- Jasper County
- Cass County
- Platte County
- Franklin County
- Christian County
- Cape Girardeau County
- Buchanan County
- Cole County
- St. Francois County
- Lincoln County
- Newton County
- Taney County
- Johnson County
- Pulaski County
- Phelps County
- Callaway County
- Camden County
- Pettis County
- Webster County
- Butler County
- Howell County
- Lawrence County
- Warren County
- Scott County
- Laclede County
- Barry County
- Lafayette County
- Polk County
- Stone County
- Stoddard County
- Marion County
- Dunklin County
- Texas County
- Miller County
- Adair County
- Audrain County
- Randolph County
- McDonald County
- Washington County
- Saline County
- Ray County
- Crawford County
- Henry County
- Morgan County
- Clinton County
- Benton County
- Nodaway County
- Vernon County
- Wright County
- Perry County
- Ste. Genevieve County
- Andrew County
- Pike County
- Dallas County
- Cooper County
- Bates County
- Moniteau County
- New Madrid County
- Macon County
- Cedar County
- Dent County
- Livingston County
- Gasconade County
- Pemiscot County
- Osage County
- Madison County
- Douglas County
- Linn County
- Mississippi County
- Barton County
- Montgomery County
- Wayne County
- Ripley County
- Bollinger County
- Ralls County
- Howard County
- DeKalb County
- Lewis County
- St. Clair County
- Grundy County
- Iron County
- Ozark County
- Caldwell County
- Monroe County
- Hickory County
- Oregon County
- Daviess County
- Maries County
- Carroll County
- Harrison County
- Dade County
- Chariton County
- Shannon County
- Clark County
- Gentry County
- Reynolds County
- Shelby County
- Sullivan County
- Carter County
- Atchison County
- Scotland County
- Putnam County
- Holt County
- Schuyler County
- Knox County
- Mercer County
- Worth County