There was no room in any campgrounds in Yellowstone for the first two nights I planned on being there, because they were all booked up except for the first-come-first-serve campgrounds, which were all too far away from where I wanted to be. I drove in from West Yellowstone, down along several rivers to end up at Old Faithful. Along the way I saw some cool waterfalls, swimming holes, elk, and hot springs.
More pictures on the full post.
I photographed many elk too and of course didn’t have a big enough zoom lens, but this one let me get pretty close and seemed vaguely interested in what I and a fly fisherman were doing nearby.
Old Faithful was really neat to see at night. There were no crowds. The steam was lit up by moonlight. I counted at least 4 shooting stars while I waited for it to blow. Lots of couples spending the night at the lodge where there was a piano player and a grand foyer with 3 levels of people lounging around. It was pretty steamy! 
Wow! Looks as beautiful as you hoped it would be.
Have Fun.
Amazing photos!!! And the medow/river is the exact shot I was telling you about!! Wish I was there !!