Fishing Bridge is the only campground in the park with hookups. But many people don't like it because it's like a big parking lot. Of course you will mostly be sleeping there so if you need hookups, that's the only game in the park. We stayed at Madison. No hookups but you can run your generator during certain hours. It was pretty centrally located. In August there are many choices. We we there in May and only 4 campgrounds were open.If you don't already have reservations for August, you will be lucky to get a site for several days.And the park will be packed. It will take longer to get any where.In May,we had no traffic jams and crowds were light.Yellowstone is huge. We were there 4 days and could have used 2 more.