OK... I'll chime in. Here are four mystery waterfalls, along with four hints:
A. All four are described in Greg Plumb's books (though there are no photos of any of them).
B. None of them are in the Gorge or Mount Hood NF.
C. One is located near the Oregon Coast.
D. There are no trails leading to any of them.
(Bryan, you are familiar with #1.)
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Greg Lief
LiefPhotos.com
OregonWildflowers.org