We arrived 11:30pm, the day of, and were still able to find a lovely spot. Every single campground has a view of the reservoir. Each has a large, cement fire pit with a cooking grate, a large picnic table, and cement patio. The rangers are there 24 hrs and are very friendly and helpful. All our neighbors were wonderful and helpful too, it attracts a nice crowd. There were lots of families and singles, a complete mix. Plenty of trees for hammocks too.
There are two RV campgrounds when you first arrive at Jordanelle, but this one is a short, 3 minute walk up a trail from the main parking lot. That means there is generally plenty of availability and lots of seclusion from the large boating parties.