Tim - I found this campground on the NPS Web site, and I tent camped there in July 2004.
If you want go get away from it all, this is the place to go. City of Rocks is a National Reserve. The camping is primitive. They have vault toilets. The campsite are very private, and most are located off the main road, which is a dirt road. City Of Rocks is an amazing grouping of granite rocks and cliffs. Its beauty rivals Yosemite. There are wonderful hiking trails for great views and nature walks. This campground is not crowded. If you are a rock climber, this is the place. If you are not a rock climber, it is still worth a couple of days hiking. Note that there is nothing for miles around. Plan on bringing what you need. Not a good campground for large RVs as the campsites are small and many are tent only.