Photos from this trip can be found here.
Koppen Mountain marked last of the Mountaineers Teanaway 20 peaks pursuit. We started from the Boulder DeRoux trailhead and crossed the bridge. At the first trail junction we got on the Middle Fork Teanaway Trail and followed it all the way to the pass. Once on the pass, we made a left and began traversing southeasterward on the northwest ridge.
A faint hikers path on the ridge got us all the way to the summit. The higher we got, the more defined the path became. Great views on top as in any other Teanaway peaks.