O'Neil Creek Campground is part of Olympic National Park, situated along the O'Neil Pass Trail that leads to the park's Enchanted Valley. The campsites are hike-in only and dispersed, with no amenities. Most spots are next to the river, offering a scenic view in one of the park's most beautiful areas.
O'Neil Creek is a popular spot for hikers headed to the Enchanted Valley as it is basic the half way point. The best campsite is the furthest back one under the maple tree. You have hang food up on the bear wire. If you are a hammock camper there are plenty of trees here to strap to. The creek is cool and refreshing.
If you're not too tied I would recommend continuing down the trail an extra mile or so to Pyrites Creek as it is typically less crowded.
This campsite is 6.9 miles up the trail to Enchanted Valley, which has to be one of the most visually stunning places on earth.
According to the campsite map, there's only 4 spots here. But on the Saturday before Memorial Day, there had to be at least 10 groups camped here (even some morons who pitched their tent directly below the bear wire). Even with the crowd, the place was free of trash (and bears) and was quiet.
Pros: Most of the spots are right next to the river, so you can fall asleep to the sound of whitewater. Lots of flat spots. A few trees for hammocks. A privy. Bear wire. Easy river access for getting water. Clean.
Cons: None really, although I'll probably camp at one of the well-established dispersed sites within a few miles of O'Neill next time. There are some awesome-looking spots with relative privacy.