Illinois Well Data · Well logs
Illinois well logs
Every time a well is drilled in Illinois, the driller files a completion report — the well log — with the Illinois State Geological Survey water well records. We hold 307,537 of them and rebuild this index weekly, so you can find one by address instead of by record number.
✓ Verified against ISGS · 2026-08-20
Well logs are filed by location, not by house number. Enter any Illinois address and we'll pull the recorded wells around it — every Illinois water well record carries a mapped location, but the state files wells by section and township rather than by street address, so results show the records around a property rather than a single wellhead.
Free address lookup Full property report — $29What's in a Illinois well log
Not every filed report carries every field — older logs are thinner, and what the state captured changed over the decades. This is the actual coverage across all 307,537 records, so you know what to expect before you look anything up.
| Field | What it tells you | Records with it | Coverage |
|---|---|---|---|
| Original log document | A direct link to the ISGS copy of the filed log itself. | 307,537 (100%) | |
| Mapped location | Coordinates, so the log can be found by address instead of by record number. | 307,521 (100%) | |
| Total depth | How deep the hole was drilled, in feet. | 301,997 (98%) | |
| Date completed | When the well was finished and the log filed. | 289,449 (94%) | |
| Driller | The licensed company that drilled the well and signed the log. | 282,111 (92%) | |
| Tested yield | Gallons per minute the well produced on the driller’s pump test. | 172,029 (56%) |
When Illinois's wells were drilled
Dated logs by decade of completion (289,449 of 307,537 records carry a usable completion date). The shape of this chart is mostly the history of the filing requirement, not of drilling — thin early decades mean the logs weren't kept, not that nobody drilled.
| Decade | Logs filed | |
|---|---|---|
| 1850s | 2 | |
| 1860s | 5 | |
| 1870s | 14 | |
| 1880s | 30 | |
| 1890s | 149 | |
| 1900s | 609 | |
| 1910s | 713 | |
| 1920s | 966 | |
| 1930s | 2,316 | |
| 1940s | 10,308 | |
| 1950s | 7,357 | |
| 1960s | 16,490 | |
| 1970s | 71,489 | |
| 1980s | 44,549 | |
| 1990s | 64,041 | |
| 2000s | 46,085 | |
| 2010s | 18,347 | |
| 2020s | 5,979 |
Three ways to find a well log here
- By address — the free lookup maps an address to the wells recorded around it. This is what most people want: "how deep is the well on the place I'm buying."
- By county — each county page carries the median depth, water level and yield computed from every log filed there, plus the drillers working it.
- By driller — every log names the company that drilled the well, so the 804 Illinois drillers in our directory each have a profile built from their own filed logs.
Well logs by county
See all 102 Illinois counties →
Where these records come from
All of it is public record from the Illinois State Geological Survey's water well records, the state's official archive of well logs filed since the 1800s (isgs.illinois.edu/groundwater/well-records). We don't hold anything the state doesn't publish. More on that database and what a filed record carries: ISGS well records. What we add is that the records are indexed by location, the statistics are computed the same way in every county, and the whole thing is refreshed weekly. Our filters and the exact computation are on the methodology page (statistics use ISGS water wells; engineering, mineral and stratigraphic test borings, mine shafts, outcrops and monitoring wells are excluded, as are wells the survey records as plugged; depths 0-5,000 ft).
Common questions
Yes. Illinois drillers are required to file a completion report for each well, and those reports are kept by the Illinois State Geological Survey water well records. Anyone can look them up. This site is an independent index of that public record — we re-read the source and recompute every page weekly.
Well logs are filed by location, not by street address, so you search the map rather than a house number. Enter the address on our free lookup and you'll see the recorded wells around that spot — every Illinois water well record carries a mapped location, but the state files wells by section and township rather than by street address, so results show the records around a property rather than a single wellhead. Each one shows its depth, static water level, tested yield, and a link to the original filed log.
The oldest dated log in our copy was completed in 1850; the newest is from 2026. Coverage thins out the further back you go — older wells were often never filed, and filing requirements tightened over time.
Most likely it was never filed. Wells drilled before the state's reporting requirement — and hand-dug or unpermitted wells — have no log at all. It also happens that a log exists but its recorded location is off, in which case it will show up under a neighboring property. Neither is something we can fix from the source data, and we'd rather say so than invent a record.
The useful parts for a buyer or a homeowner: how deep the well is, how high the water stands in it, how many gallons per minute it produced when tested, what the driller hit on the way down, and who drilled it. Together those say whether the well is likely to keep producing and what a replacement would cost.
The property report pulls every recorded well near an address — depths, water levels, yields, drillers , and links to each original filed log — as one printable summary for due diligence.
Property report — $29Driller, agent, or inspector pulling these regularly? Unlimited & white-label plans →