My guess is Whetstone Mountain Trail.

Nope. The trail in question is much lower.

How about Alder Flat?  That's a pretty low trail.

kirk said
How about Alder Flat?  That's a pretty low trail.

I'll call that close enough. Its actually the next section (or remnant) of the original Clackamas River Trail upstream.

Your turn to post.

Bryon Boyce said

I'll call that close enough. Its actually the next section (or remnant) of the original Clackamas River Trail upstream.

So where is this mystery trail?   I looked a bit at the old maps and don't recognize anything other than the "phantom" trail that shows on the current mytopo maps that was never built that went south from Indian Henry.

Its on the Riverside section of the trail along the Clackamas River south of Riverside Campground. There are discontinuous segments of trail scattered along the Clackamas from Alder Flat South, some of which still show up on the current forest service maps.