Yellowstone is one of the more frequented parks. You will see a ton of RV's and about 1,000 people to every bison it seems like. That said, Mammoth is a great location for your first nights stay if coming in through the parks North Entrance, as we did. Grabbing a site so close to the entrance made it possible to take our time in that region of the park for a day until moving on to the next. The hot springs are very interesting. There is a wooden boardwalk for viewing them. The campground itself has a lot of sites (over 80 if I recall correctly) and the fee is $20 per night. We discovered it is open year round which would be great for winter camping in the area. You cannot reserve sites here so you will need to get in early. It was only about half full when we were there in August which really surprised us.