When/how to book Yellowstone

RGar974417 wrote:
We're going in May. I booked last fall. Only 2 campgrounds open at that time but had no problem getting a site Wednesday through Sunday in Madison. My experience is if you go in on a Sunday or Monday though Thursday,it's easier getting a site than on a weekend.

Weekends make no difference in Yellowstone or Glacier. There is no population center anywhere near those two parks, all the visitors come from a long way away. They are not weekend getaways, they are destinations for vacations. If anything, there are less visitors Saturday and Sunday, since those are travel days for people coming and going home from distant cities.