Published August 15, 2026
Clearest Lakes in America 2026: Ranked by Secchi Clarity
8,685 graded lakes across the 36 states and 2 Canadian provinces carry a Secchi clarity reading. 418 of them clear 20 feet or more. These are the 20 clearest among fully graded lakes — ranked by measured visibility, not travel-brochure photography.
The 20 clearest graded lakes by Secchi depth
Cadden Lake leads at 57.4 feet of Secchi clarity with an overall grade of A. The top twenty average 40.7 feet of visibility — the kind of water where a kayak paddle looks painted underwater. Lakes with a Secchi reading but no full A–F grade are excluded here so every row carries both clarity and a water-quality grade.
| Rank | Lake | State | Clarity (ft) | Grade | Area |
|---|---|---|---|---|---|
| 1 | Cadden Lake | ON | 57.4 | A | - |
| 2 | Crescent Lake | OR | 51.7 | A | - |
| 3 | Greenwater Lake | ON | 47.9 | A | - |
| 4 | Fremont Lake | WY | 42.8 | B | - |
| 5 | George Lake | ON | 42.7 | A | - |
| 6 | Killarney Lake | ON | 42.7 | A | - |
| 7 | Osa Lake | ON | 42.7 | A | - |
| 8 | Kearney Lake | ON | 41 | A | - |
| 9 | Pog Lake | ON | 40.4 | A | - |
| 10 | Costello Lake | ON | 40 | A | - |
| 11 | Clear Lake | ON | 39.4 | A | - |
| 12 | Norway Lake | ON | 39.4 | A | - |
| 13 | Lake Desmet Lpd | WY | 39.1 | B | - |
| 14 | Basswood Lake | ON | 37.7 | A | - |
| 15 | Blue Lake | ON | 37.7 | A | - |
| 16 | Sunset Lake | VT | 36.1 | A | - |
| 17 | Sandford Lake | ON | 34.8 | A | - |
| 18 | Lake Desmet Rtpd | WY | 34.6 | B | - |
| 19 | Lac de la Ferme | QC | 33.5 | A | - |
| 20 | Lac Couture | QC | 33.3 | A | - |
The live table — updated whenever the monitoring refresh ships — is at /ranking/clearest. For the single clearest lake in every county we track, see The Clearest Lake in Every County.
What “clear” actually measures
Secchi depth is a transparency test, not a toxicity test. Clear water usually means low algae and low suspended sediment, which is why clarity correlates strongly with A and B grades. But tannin-stained lakes in forested watersheds can look tea-colored while still scoring well on phosphorus and chlorophyll-a, and a recently wind-stirred shallow lake can temporarily lose feet of clarity without a nutrient problem. That is why LakeQuality publishes both a clearest ranking and a cleanest (combined grade) ranking.
- 3,213 lakes in the dataset clear at least 10 feet — a practical threshold for comfortable swimming visibility.
- 418 lakes clear 20 feet or more — the glass-water tier travel sites market as “crystal clear.”
- Grade still matters: a clear lake with rising phosphorus is an early warning, not a forever passport.
Why travel listicles and our ranking disagree
Magazine and affiliate roundups for “clearest lakes in America” usually pick photogenic destinations — Tahoe, Crater, George, Chelan — and cite a handful of historic clarity records. Those lakes earn the reputation. Our ranking answers a different question: among the monitored lakes we grade today, which have the highest recent Secchi readings? That surface favors less-famous oligotrophic lakes that rarely appear in Travel + Leisure but do appear in EPA and state monitoring files. Both answers can be true; only one is reproducible from a public dataset this size.
For the science of the measurement itself, read Water Clarity Explained. For how clarity feeds the A–F grade, see Lake Water Quality Grades Explained.
Frequently Asked Questions
Among lakes we grade with Secchi measurements, Cadden Lake in ON currently leads at about 57.4 feet of visibility. Famous alpine lakes outside our monitoring join can be clearer still — this list is the clearest water we can prove from the graded dataset.
No. Clarity is one of three grade inputs. A lake can be very clear yet still carry elevated phosphorus, or look murky from tannins without high algae. Cleanest ranks the combined grade; clearest ranks Secchi depth alone.
A black-and-white disk is lowered into the water until it disappears from view. That depth, reported in feet here, is the Secchi reading — a standard field measure of water transparency used by state agencies and the EPA Water Quality Portal.
Those lakes are extraordinarily clear and closely monitored by park and university programs. Our ranking only includes lakes that appear in the graded LakeQuality dataset with a usable Secchi metric. If a famous lake is missing, it is a coverage gap in that join — not a claim that it is murky.
/methodology
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