We accidentally discovered Gnat Creek when we needed a place to stopover on a return from Astoria. There isn't a ton here, but there are the necessities - a place to put your tent for the night and a bathroom.  We also took advantage of where we wound up and did a short hike which led to a fish hatchery. 

Camping here is all first come and tent—but it's not really the kind of site you'd book in advance anyway.