Pretty nice gravel most of the way with relatively low grade climbs (around 3% grade for the most part) EXCEPT for a short stretch near the turn around point that was a bit crazy (mostly single track, dirt, and extremely steep - 15-20% grade for much of the way). There are routes that can avoid that crazy part, but I understand that they all take you on private property. Just take it slow and you'll be fine. If you're doing an OAB ride, the climb back up the crazy section is, well, crazy. We started at a trailhead lot a few miles up the Skamania/Vernonia Highway (but you can start at the very beginning of the trail in Scappoose if you don't mind a few trash miles on the least scenic section of the trail.