Skip to content
RADON411

Locations and reports

Radon Levels in Crook County, Wyoming

EPA puts Crook County in Zone 1, its highest radon zone, and high results are common there: 58.8% of the 51 radon tests reported to CDC (2008 to 2017, laboratory totals) came back at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    58.8%

    14.5 pts above WY

    Crook
    58.8%
    Wyoming
    44.3%

    51 tests, 2008 to 2017

  • Median result

    5.1pCi/L

    Action level reached

    Crook
    5.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    51

    21st of 22 by tests

    Crook
    51
    Laramie
    1,834

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Wyoming

    5 of 22

    Top quarter

    Crook
    58.8%
    Sheridan
    69.5%

    By share, of 22 with 30+ tests

Read a result for Crook County

Starts at Crook County's median, 5.1 pCi/L

5.1pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 5.1 pCi/L

At or above 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher. Crook County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Crook County, At a glance

Crook County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Crook County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

USGS geologic potential: Moderate across 55% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Crook County, 2008 to 2017, laboratory

Reported results by concentration band, Crook County, 2008 to 2017, laboratory
Under 2 pCi/L: 23%2 to 4 pCi/L: 18%4 pCi/L and above: 59%

Of 51 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Crook County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L1223.5%
2 to 4 pCi/L917.6%
4 pCi/L and above3058.8%
What these figures count

These are the 51 tests reported to CDC for Crook County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.

Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Crook County, Compared

Crook County radon figures, compared

Calculated by Radon411

More than half: 58.8% of the 51 radon tests reported to CDC for Crook County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 5th of 22 Wyoming counties with 30 or more tests for the same period. That is 14.5 points above the 44.3% pooled from 23 Wyoming counties.

The median result, 5.1 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 28.4 pCi/L. The rest split 23.5% under 2 pCi/L and 17.6% from 2 to 4 (Wyoming: 25.5% and 30.2%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 58.8% share point the same way here.

1 of its 3 bordering counties with figures ran higher, led by Weston County at 65.6%; Campbell County reported 43.9%. Statewide for the same period, Sheridan County reported the highest share (69.5%) and Uinta County the lowest (24.6%).

CDC's ten-year totals for Crook County went from 38 tests (2005 to 2014) to 51 (2008 to 2017), the share going from 63.2% to 58.8%.

Nationally, every county with a figure for the same period pools to 35.7%; Crook County sits 23.1 points above it.

Crook County against Wyoming, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Crook County
Crook County5158.8%5.1 pCi/LThis county
Wyoming, pooled23 counties, pooled7,63844.3%Not pooled−14.5 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−23.1 points
Sheridan Countyhighest in the state84669.5%5.8 pCi/L+10.7 points
Uinta Countylowest in the state19924.6%2.2 pCi/L−34.2 points
Weston County, WYborders it3265.6%6.3 pCi/L+6.8 points
Powder River County, MTborders it862.5%4.5 pCi/L+3.7 points
Butte County, SDborders it2458.3%5.4 pCi/L−0.5 points
Lawrence County, SDborders it16056.9%5.3 pCi/L−1.9 points
Campbell County, WYborders it27143.9%3.5 pCi/L−14.9 points
Where Crook County's reported results fell, 2008 to 2017, laboratory, beside Wyoming and the United States
ResultCrook County testsCrook County shareWyoming shareU.S. shareAgainst Wyoming
Under 2 pCi/L1223.5%25.5%39.6%−2.0 points
2 to 4 pCi/L917.6%30.2%24.7%−12.6 points
4 pCi/L and above3058.8%44.3%35.7%+14.5 points
Crook County ranked among the 22 Wyoming counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Sheridan County1 of 2284669.5%5.8 pCi/L
Lincoln County2 of 2214268.3%7.8 pCi/L
Weston County3 of 223265.6%6.3 pCi/L
Converse County4 of 2213062.3%4.8 pCi/L
Crook County5 of 225158.8%5.1 pCi/L
Hot Springs County6 of 225955.9%4.2 pCi/L
Natrona County7 of 221,05455.7%4.3 pCi/L
Fremont County8 of 2261855.7%4.7 pCi/L
Sublette County9 of 226050.0%4.0 pCi/L
Sweetwater County10 of 2240949.6%3.9 pCi/L
Teton County11 of 2227844.6%3.4 pCi/L
Crook County ten-year laboratory totals, against Wyoming's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestWyoming, pooledChange from the row before
2008 to 20175158.8%5.1 pCi/L28.4 pCi/L44.3%−3.2 points
2007 to 20165062.0%4.9 pCi/L28.4 pCi/L44.6%+4.9 points
2006 to 20154257.1%4.4 pCi/L28.4 pCi/L45.3%−6.1 points
2005 to 20143863.2%4.7 pCi/L28.4 pCi/L45.5%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Crook County, Geology

The ground under Crook County

Predicted

USGS's geologic map splits Crook County: 54.7% of its land is moderate radon potential and 45.4% high. The map puts 41.9% of Crook County in the area it calls Black Hills and 37.0% in Black Hills, with 2 smaller areas beside them. USGS gives the first a radon index of 12, in the high band (12 to 17), and the second 11, in the moderate band (9 to 11).

USGS's geologic areas under Crook County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Black HillsLate Paleozoic sedimentary or Precambrian intrusive igneous rocks.High1241.9%
Black HillsLate Paleozoic sedimentary or Precambrian intrusive igneous rocks.Moderate1137.0%
East Powder River BasinUpper Cretaceous marine sedimentary rocks.Moderate1117.6%
Powder River BasinCretaceous and Tertiary uranium-bearing marginal-marine and fluvial sandstones.High123.5%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Crook County beside the ground around it

Wyoming as a whole has more high-potential ground than Crook County: 72.4% of its land, against 45.4% here. Of the 6 counties that border it, 2 have more high-potential ground, Campbell County the most at 97.6%.

Share of land by USGS radon potential: Crook County, the 6 counties bordering it and Wyoming
AreaEPA zoneLow potentialModerate potentialHigh potential
Crook CountyZone 1None54.7%45.4%
Lawrence County, SDZone 2None89.5%10.5%
Campbell CountyZone 1None2.4%97.6%
Butte County, SDZone 2None82.2%17.8%
Carter County, MTZone 1None76.1%23.9%
Weston CountyZone 2None54.9%45.1%
Powder River County, MTZone 1None16.4%83.6%
Wyoming23 counties, pooled by land areaVariesNone27.6%72.4%

The map rates the ground, not the air in any home.

Local help

Crook County, Local resources

Radon testing and mitigation in Crook County

What it means

Crook County, Questions

Questions about radon in Crook County

Are radon levels high in Crook County?

Over the 2008 to 2017 laboratory totals, 58.8% of the radon tests reported to CDC for Crook County, Wyoming were at or above 4 pCi/L, and the median reported pre-mitigation result was 5.1 pCi/L. Of 22 Wyoming counties with 30 or more tests for the same period, 4 reported a higher share; pooled, the state comes to 44.3%.

Which counties border Crook County?

Crook County borders 6 counties: Lawrence County, SD, Campbell County, WY, Butte County, SD, Carter County, MT, Weston County, WY and Powder River County, MT.

Products

Crook County, Products

Testing a home in Crook County

In Crook County, 58.8% of 51 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 44.3% pooled across Wyoming. In Zone 1 the year-round level in Crook County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.

Test kits and monitors3

See every kit and monitor

Crook County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Crook County

Explore

Crook County, Bordering counties

Counties bordering Crook County

Calculated by Radon411

Crook County, Cities and towns

Cities and towns in Crook County

Crook County is growing: the Census Bureau puts it at 7,852 residents on July 1, 2025, up 9.3% from 7,183 in 2020. Spread over its land, that is 2.8 people to the square mile. No town dominates: Sundance, the largest, has 1,141 residents, 14.5% of the total. Together its 4 incorporated places hold 39.4% of those residents; the other 60.6% live outside any of them. Reported testing is thin here: 51 tests over 2008 to 2017, or 6.5 for every 1,000 residents (2025 estimate), where Wyoming as a whole comes to 13.0.

From Sundance to Hulett, CDC publishes no figure by town: each reads Crook County's.

The cities and towns in Crook County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Sundance1,141+10.6%14.5%
Moorcroft1,023+8.5%13.0%
Pine Haven579+16.3%7.4%
Hulett349+12.2%4.4%

4 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).

Crook County, Homes

Homes in Crook County

Of Crook County's 3,673 homes, 74% are detached houses, against 68% across Wyoming; 20% are mobile homes. Half of its homes were built before 1987, close to Wyoming's 1980: 14% date from before 1960 and 34% from 2000 or later. Owners live in 76% of the occupied homes (Wyoming: 72%), so for most households a test and a fix are their own to order.

Homes in Crook County, Wyoming, 2019 to 2023
HomesCrook CountyWyoming
Housing units3,673275,131
Detached houses74%68%
In buildings of 5 or more3%9%
Mobile homes20%12%
Built before 196014%24%
Built since 200034%24%
Middle year built19871980
Owner-occupied76%72%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.