There are 2 entrances but the physical addresses is 5000 East Entrance Road Paicines, CA 95043. If you navigate to 2400 Hwy 146 Pinnacles Area, Paicines, CA 95043, you will get to the east entrance
Being genuine, plug in Pinnacles Campground into Google and it takes you exactly where you need to be. I say this because I did it last weekend and it nailed it. Once you get off the main road it's very intuitive to get to the grounds with plenty of signage.
To add to what Jonathan Wong said: The East entrance is the main entrance, with the camp ground and information center, etc. The west entrance there is a ranger that will take your payment to get in and give u a map, answer questions. Etc. But other than the ranger check in there is only hikes from the west. And a bathroom and water fill up station
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