Yellowstone National Park

I'm leaving for my cross-country road trip in 1 week!! I'm excited to see all the beautiful places that the USA has to offer. I'm glad that I'm not going abroad to backpack Europe, as many post-college kids do. That was the original plan, but considering that I'm broke, road trippin' around the USA seemed doable.  I've never been west of Chicago, so I am very excited to venture all the wall to the Pacific. One of the places I'm most excited to see is Yellowstone. I will be there over Memorial Day Weekend, and it's sure to be a packed park. I'll be attempting to get a first-come, first-served campsite. Which campground would you recommend?

Please do share your experiences visiting Yellowstone in the comments below!