Yesterday I found an excellent article by Kurt Repanshek about booking rooms in prime locations in various national parks, with an emphasis on Yellowstone and its wonderful Old Faithful Inn. Agreeing with everything I read there, I was going to write a short comment to say so and found that the well-known environmental historian Alfred Runte had written essentially what I would have commented.
I have had very much the same experiences as these two men have had and can only add that, especially for Old Faithful Inn, you should book a year or more in advance of your visit. However, I’ve sometimes had good luck calling a day or two before I needed a room and learning that a cancellation has created an opening.
The entire article and comments are on the National Parks Traveler site.