Madrona Campground is a small and free camping spot lying on the Middle Fork of the Smith River just off of the highway. From the sites you can access the water very easily.
The campground itself is very limited in amenities, but it has great river access and it is close to popular attractions in the area like Panther Flat and Sandy Beach swimming holes. In total, there are only three established sites to choose from. After taking the short road off of the highway, the first site will be on your right side. This site is basically on the road, but is closest to the toilets and river trail access. If you turn the corner, two more sites will pop up in a much more private setting. These sites are a stone's throw from the river.
While it is right next to the highway, it does see much less foot traffic than the surrounding attractions, making it a great last minute spot if other campgrounds are already taken or if you prefer the small campground vibe.