Go to NPS.gov. It will show you all of the National Parks. Most sites in the parks do not include hookups. I would get an Atlas of the western US, highlight all of the national parks, look them up on NPS.gov and print out the maps and info on each park. I do not think that 4 days at each park is a good idea. Some you can do in 1 or 2 days and Yellowstone is probably worth more than 4, if your time allows for it. We are headed for Yellowstone for the eighth time this September and planning on 12 days. Baker Hole in the National Forest is 5 miles north of West Yellowstone and has electric and water hookups.