I'm planning a trip late spring thru South Dakota and to Yellowstone. I will be pulling my Aspen camper and would like to hear from anyone who has camped at Yellowstone as to the camp sites and do I need to make reservations. I also would like to know when the roads are most likely to be free of snow and ice, hoping to beat the summer crowd. Any information related to roads, attractions or camping spots would be appreciated. Thanks, Gordon