This is a relatively small campground and fills up quickly during the summer so my advice is to get there early to be able to secure a campsite. What can I say? It's all about camping by the ocean! Be prepared for weather changes and cooler weather,it can change rapidly. Be prepared to be lulled to sleep by the sound of the waves crashing against the shore!
We camp here as much as possible. Just good ol' pit toilets, but usually not crowded, and very quiet. As Humboldt locals, we like to be away from the crowds, in the most beautiful natural areas in California. This is the trail head to the famous Lost Coast Trail, and just a stunning beach campground. Dogs allowed on leash, pop your tent in the sand. Super nice.
No big stores nearby, so you should probably get groceries in Eureka or Fortuna before heading over the hill to Petrolia. There is a small store, but this is Humboldt so they could be closed at any given point, wouldn't depend on it.
Be careful in the summer, not really sandal appropriate. The native dune plants have lots of little prickers in the sand among the campsites.
Make sure to stroll along the beach north to where the Mattole river flows into the Pacific. You will almost always find a bunch of seals hanging out on the other side of the river spit and hunting in the estuary for fist.
It's a journey to get here, and well worth it. A small, secluded campground with access to a broad sandy beach. Nice pit toilet.