On the McCloud River, within hiking distance of the three waterfalls. Apparently heavily used in the swimming months, but pleasantly uncrowded tonight. The hike to Lower Falls is less than a mile and very scenic. Hike to Middle/Upper Falls is a little more than a mile. You can walk the paved road back to make it a loop if you wish.
Way overpriced and has stupid rules. The park borders the Wabash River, but the campground itself is miles from the river. There is a public swimming pool that is an additional charge on top of the camping fee.
Due west of Chico, about 12 miles on the west side of I-5 is Black Butte Lake. It has two ACE campgrounds, this is the secondary one, it closes in early September. It's a few miles closer to Orland and on a bluff 100 or so feet above the water. Very pleasant.