What type of map is most useful for a person hiking
along the appalachian trail?

Recommend using Guthook’s AT Hiker App (iOS, Android), which is quite useful if you want to pinpoint your location along the trail with a Smartphone GPS (which can still operate when it’s not connected to cell phone service.) It’s better than carrying a trail map because it’s always up-to-date and the app lets you share information with other nearby hikers (like local Wifi passwords, the location of good campsites, water availability, and shelter conditions) using a virtual trail register capability. While you can carry a paper version of the AT Guide or tear out pages from it, I refer to a PDF version of it and Guthook’s App on my smartphone. Like it or not, a smartphone has become an essential on the Appalachian Trail. (See the Appalachian Trail Cell Phone Guide)