Yellowstone National Park

Between Teton np & Yellowstone np there's a small strip of private land & Flagg ranch campground were a gravel road run there are national forest campgrounds (3 or 4) spots at each site .they are placed about a mile apart down that gravel road. These cg have potapotties & fire rings. No water. They are first come. There are also a bunch of national forest cg along road outside the west entrance to Yellowstone.

I was there last summer. We stayed at the madison river campground, and the norris campground. Our trip was mostly a fishing with a little bit of sightseeing. We probably drove 600 miles while in the park. If you don't have reservations at any and you want to stay in the park, arrive at the campground early. Most of them fill up before 11am. We just drove from each of these campgrounds to our destinations .   The rush to obtain non Reserva be campsites is like black Friday sales.

If there are certain areas in the park you want to see, it is best to go early or late. Traffic in the park at midday is very busy.

On the other hand, it is one of the most beautiful places on earth. I'm planning to go back next summer.

Grand Teton and Yellowstone NPs are beautiful, but yes, they do get crowded. I haven't been down that way in a while although I've lived in Montana the last 45 years. There are lots of national forests in Wyoming and Montana with nice campgrounds that don't get as much visitation as the parks...still beautiful scenery, wildlife, etc. And they are dog-friendly...thinking about your Labrador child, Misha. I have a Lab too.

Gros Ventre (properly pronounced "grow vont") campground is a nice big campground north of Jackson on the Gros ventre river, huge flat valley with mountains on both sides, with a big sagebrush flat out front and the Tetons about fifteen miles to the west.  Spectacular views.  Fantastic in September or mid May.  But again, later on in summer you get to deal with high volumes of traffic out of Jackson headed to Yellowstone. Jackson actually has traffic jams daily in the summer.  Like all day long.  It is a place to avoid imo.   If you are city people, I guess you can deal with it.  I am not one of those city  folks, and I thoroughly avoid anything in the Teton valley, Jackson Hole country, and the south gate of Yellowstone park in the summertime because of decades of experiences doing it.  Plus with the tour busses coming in from Salt Lake City and elsewhere it is a mess trying to drive up to the park from there.  Now you have been warned twice about it by someone who lives here.   I'm trying to help make your trip a good one.   

There are both private and U.S. Forest service campgrounds outside the park at every entrance.  Colter Bay in Grand Teton park is beautiful with the lake and the Tetons out front there, but for travelling into the park for day trips the south entrance has the horrific Jackson Hole traffic and traffic jams.  I would not stay there in the summer if I were going into Yellowstone.  September on I would.  The east entrance into Cody, the west entrance at the town of West Yellowstone, or the much quieter north east entrance at Cooke city Mt. all have some great places to camp just outside the park.   I live outside the east entrance but have camped at all of the areas mentioned.  Good luck deciding.