Just after crossing into Yellowstone at the northern most outlet you will find Mammoth Hot Springs Campground, one of the most convenient and ONLY campground where you will find most of the comforts of home aka cell service. Sure for those not caring about this service the campground might not be the most appealing as it is harder to get into because of prebooking, but for those who year round are looking for a convenient location with room to enjoy the local Fort Yellowstone area this is where it is at.
So with the added amenity of having coverage you might expect this to be one of the higher priced campgrounds, but the price of only $20 per night is extremely reasonable.
There are no showers at this campground, however the bathroom facilities are very nice with flushing toilets and cold water in the sinks. I found this to be one of better campgrounds when it came to bathrooms as they seemed larger than most.
Another unique feature of this campground was that a certain number of sites are set aside for those cycling of hiking the area, a very important feature considering so many visit this area on the Contential Divide Trail. Also there are a select amount of accessible sites for handicapped featuring raised tent pads and water access which is right in the campsite instead of elevated on the hillside like some.
For those not wanting to book in advance, this campground fills very quickly. I noticed that on weekdays the few sites reserved for day of use filled before noon, so make this your first stop of the day instead of exploring the park first.
Pull ins seemed large enough for mid to large units and the only thing I could say that might be a negative to those in larger units is that you are right on the roadway in some campsites if you are a big rig. There are a few sites which have size restrictions so check on these before visiting.
For tent campers like myself the pull ins allow you plenty of room to spread out and enjoy yourself. Sites include picnic tables, bear boxes and fire rings.
In this area during the late summer and early fall you are likely to find elk very nearby, they tend to come down and graze in the area of Mammoth Hot Springs. During these times you want to make sure you are remembering to stay at least 25 yards away from them and if you hear them they are likely protecting young or looking to mate so this is when they are more aggressive. Being able to see them in person is something majestic however!!
Check out the visitor center at the Mammoth community / Fort Yellowstone. this center in my opinion was one of the more interesting when it comes to the history of the park.
Visit the Hot Spring at sunset, it is something spectacular at any time of day but at this time as the clouds paint the skies it is the perfect photo opportunity.
If you are visiting the park for only a short time, use the internet access at the camp to plan your time, this will really allow you to find the parts of the park you are interested in rather than having to pull off at each point to determine this.
Remember west side of the park is more about the geothermal features, it is also the more crowded portion of the park.