From Dufur, go 15 miles west on Forest Road 44. Campground is on the south side of FR 44.
Off the beaten path but just off the road, peaceful and idyllic in the winter
Underhill is a strange Forest Service campground. It doesn't have an official sign, nor does it appear on the website’s list of campgrounds. And yet here it is: a scruffy, seemingly much-ignored patch right off the Dufur Valley Road. When I visited, the vault toilet's lock was broken and the steel door had some sizable bullet holes in it. It was, however, a clean facility, and someone had even put a lined trashcan inside. The two (or is it three?) campsites are austere — not many trees, no nearby body of water, no privacy and no particularly compelling views— but there is that building, which has a fairly decent roof over it, a massive picnic table inside, and a seriously burned-out wood stove that no one should even think of using.
I'd pitch a tent here if Eightmile, Lower Eightmile, Pebble Ford, Knebal Springs and Fifteenmile were all full, and I didn't bring the necessary for dispersed camping. Call it a fallback-fallback-fallback option. On the upside, it's free!