This year the National Park Service (NPS) celebrates its 100th birthday. Over the past century, the agency has protected and managed a system that has grown to now include 59 parks in 27 states and ranges from famed summer-vacation destination icons like Yellowstone and Yosemite to the remote 8.4 million wild acres of Alaska’s Gates of the Arctic and tropical paradises like Florida’s Dry Tortugas. Of course, the parks can be popular, but don’t let that scare you away this summer. The best way to truly immerse yourself in these wild landscapes is to get away from the gawking roadside crowds and spend days exploring their deep, primal secrets by foot. To that end, and to celebrate a hundred years of the NPS, we offer up these best ten backpacking trips in the parks.