Village, Ogle County, Illinois
Radon Testing in Stillman Valley, IL
Updated
IEMA has 112 radon test results on record for Stillman Valley. 52.7% came back at or above the EPA's action level of 4.0 pCi/L. That is close to the Ogle County rate of 49.7%. A standard test runs $150 to $300. The only way to know about one specific house is to test it.
Stillman Valley sits in southern Ogle County, named for Stillman Creek and the 1832 battle nearby that opened the Black Hawk War. It has about 1,260 residents and 500 housing units packed into 0.57 square miles, by far the most densely built of the newer towns on this page, and is in the Meridian Unified School District.
What IEMA's radon test records show
Look past the median to the tail: 7.1% of Stillman Valley tests were 20 pCi/L or more, five times the action level. The top reading on record is 44 pCi/L. The average result in Stillman Valley is 6.59 pCi/L, against 5.98 for Ogle County overall. IEMA's own dataset covers tests licensed measurement professionals submitted from 2003 through July 2019, keeping only the highest reading on record per address. That means it is not a random sample and not year-by-year, but it is the closest thing to primary local radon data that Illinois publishes.
| Tests | Avg pCi/L | 4+ pCi/L | 10+ | 20+ | |
|---|---|---|---|---|---|
| Stillman Valley | 112 | 6.59 | 52.7% | 21.4% | 7.1% |
| Ogle County | 1,751 | 5.98 | 49.7% | 15.7% | 3.9% |
Source: IEMA radon test records, Illinois Emergency Management Agency.
The ground under Stillman Valley
Ogle County runs along the Rock River south of Winnebago and Boone Counties, on the same general family of dolomite and limestone bedrock, with Ordovician rock exposed in spots near the river. The EPA places Ogle County in Radon Zone 1 too, the same highest-potential category as its neighbors to the north.
Housing in Stillman Valley
Stillman Valley has an estimated population of 1,260 and 500 housing units across 0.57 square miles. That works out to about 2,211 people per square mile, well past rural density for this part of Illinois. The Census Bureau doesn't separately publish a detailed housing-age or tenure breakdown at this population size, so Ogle County's own numbers, on the other Ogle County pages on this site, are the closest real context for Stillman Valley specifically, not a figure unique to it.
Source: U.S. Census Bureau, American Community Survey 2020-2024 5-year estimates (via Census Reporter) and 2024 TIGER/Line county subdivision and place boundaries.
What we do in Stillman Valley
Radon testing, Buying or selling a home, and New construction.
Common questions
Is radon a problem in Stillman Valley?
Yes. Out of 112 IEMA-recorded tests taken in Stillman Valley, 52.7% came in at 4.0 pCi/L or higher, the EPA's action level. That fits Ogle County's overall Zone 1 rating, the agency's highest-potential class.
What is the highest radon reading on record near Stillman Valley?
44 pCi/L, out of 112 IEMA-recorded tests. That is an outlier, not typical, but it shows why testing rather than guessing matters: neighboring houses can differ by a wide margin.
We're closing on a house in Stillman Valley soon. Is there time to test?
In most cases, yes. Scheduled early in the inspection period, a short-term test (a few days to about a week) has time to come back before you need to decide anything. Details on our <a href="/real-estate-radon-testing">real estate radon testing</a> page.
Nearby
Byron (50.3% of tests at 4+ pCi/L), Davis Junction (58.2% of tests at 4+ pCi/L), Oregon (54.5% of tests at 4+ pCi/L).
Need radon testing booked in Stillman Valley?
Tell us why you're testing and any deadline you're working against. You get a fixed price and a straight answer back.