Head for the hills — South Dakota’s Black Hills — to see six National Park Service sites in a single trip. Devils Tower (in Wyoming), Mount Rushmore, Minuteman Missile, Badlands, Wind Cave and Jewel Cave are all within a few hours’ drive of one another. For budget-friendly accommodations, base yourself in any of these four Dakota burgs: Rapid City, Keystone, Hill City or Custer. Only Badlands and Devils Tower charge entrance fees; Rushmore has paid parking, while the caves charge for underground tours. Other low-cost attractions nearby include Custer State Park, where bison roam free, and the work-in-progress Crazy Horse Memorial.