The most recent statement on the length of the A.T.
http://www.appalachiantrail.org/about-the-trail
gives an answer of 2180 miles.
This means that section hikers such as myself have passed the half-way point once they have hiked 1090 miles. After my most recent multi-day hike, I calculated my total miles covered as 1081.8 -- meaning I needed just over eight miles to get to that half-way point.
Due to my (basically successful) effort to minimize difficult hiking
...