Recently updated on the National Park Services' website for the Appalachian Trail is this statement:
"Visitors may possess firearms within a national park unit provided they comply with federal, state, and local laws.
The role of the responsible gun owner is to know and obey the federal, state, and local laws appropriate to the park they are visiting. Below is a list of links to State Statutes on firearms. Please remember that federal law prohibits firearms in certain park facilities and buildings. These places are marked with signs at public entrances."
Following this is a list of links for 13 of the 14 states the AT crosses (Except Georgia) for details of local regulations of firearms.
So you can carry a gun on 25% of the AT.
Does that make you feel safe?